Added Source Code and Send Feedback buttons to About dialog (#13510)

<!-- Enter a brief description/summary of your PR here. What does it fix/what does it change/how was it tested (even manually, if necessary)? -->
## Summary of the Pull Request
Added two new buttons to the About dialog. Source Code and Send Feedback buttons link directly to the Terminal project on GitHub and to the Issues page respectively.

<!-- Other than the issue solved, is this relevant to any other issues/existing PRs? --> 
## References
#13371

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## PR Checklist
* [ ] Closes #13371
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [x] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #13371

<!-- Describe how you validated the behavior. Add automated tests wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
Performed manual testing and confirmed that the implementation works.

src/cascadia/TerminalApp/Resources/en-US/Resources.resw

@@ -436,6 +436,9 @@
   <data name="AboutDialog.Title" xml:space="preserve">
     <value>About</value>
   </data>
+  <data name="AboutDialog.PrimaryButtonText" xml:space="preserve">
+    <value>Send Feedback</value>
+  </data>
   <data name="AboutDialog.CloseButtonText" xml:space="preserve">
     <value>OK</value>
   </data>
@@ -447,6 +450,10 @@
     <value>Getting Started</value>
     <comment>A hyperlink name for a guide on how to get started using Terminal</comment>
   </data>
+  <data name="AboutDialog_SourceCodeLink.Content" xml:space="preserve">
+    <value>Source Code</value>
+    <comment>A hyperlink name for the Terminal's documentation</comment>
+  </data>
   <data name="AboutDialog_DocumentationLink.Content" xml:space="preserve">
     <value>Documentation</value>
     <comment>A hyperlink name for user documentation</comment>

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -693,8 +693,8 @@ namespace winrt::TerminalApp::implementation
 
     // Method Description:
     // - Show a dialog with "About" information. Displays the app's Display
-    //   Name, version, getting started link, documentation link, release
-    //   Notes link, and privacy policy link.
+    //   Name, version, getting started link, source code link, documentation link, release
+    //   Notes link, send feedback link and privacy policy link.
     void TerminalPage::_ShowAboutDialog()
     {
         _ShowDialogHelper(L"AboutDialog");
@@ -710,6 +710,11 @@ namespace winrt::TerminalApp::implementation
         return CascadiaSettings::ApplicationVersion();
     }
 
+    void TerminalPage::_SendFeedbackOnClick(const IInspectable& /*sender*/, const Windows::UI::Xaml::Controls::ContentDialogButtonClickEventArgs& /*eventArgs*/)
+    {
+        ShellExecute(nullptr, nullptr, L"https://github.com/microsoft/terminal/issues", nullptr, nullptr, SW_SHOW);
+    }
+
     void TerminalPage::_ThirdPartyNoticesOnClick(const IInspectable& /*sender*/, const Windows::UI::Xaml::RoutedEventArgs& /*eventArgs*/)
     {
         std::filesystem::path currentPath{ wil::GetModuleFileNameW<std::wstring>(nullptr) };

src/cascadia/TerminalApp/TerminalPage.h

@@ -251,6 +251,7 @@ namespace winrt::TerminalApp::implementation
         void _CommandPaletteButtonOnClick(const IInspectable& sender, const Windows::UI::Xaml::RoutedEventArgs& eventArgs);
         void _AboutButtonOnClick(const IInspectable& sender, const Windows::UI::Xaml::RoutedEventArgs& eventArgs);
         void _ThirdPartyNoticesOnClick(const IInspectable& sender, const Windows::UI::Xaml::RoutedEventArgs& eventArgs);
+        void _SendFeedbackOnClick(const IInspectable& sender, const Windows::UI::Xaml::Controls::ContentDialogButtonClickEventArgs& eventArgs);
 
         void _KeyDownHandler(const Windows::Foundation::IInspectable& sender, const Windows::UI::Xaml::Input::KeyRoutedEventArgs& e);
         static ::Microsoft::Terminal::Core::ControlKeyStates _GetPressedModifierKeys() noexcept;

src/cascadia/TerminalApp/TerminalPage.xaml

@@ -100,13 +100,16 @@
                        x:Uid="AboutDialog"
                        Grid.Row="2"
                        x:Load="False"
-                       DefaultButton="Close">
+                       DefaultButton="Close"
+                       PrimaryButtonClick="_SendFeedbackOnClick">
             <StackPanel Orientation="Vertical">
                 <TextBlock IsTextSelectionEnabled="True">
                     <Run Text="{x:Bind ApplicationDisplayName}" /> <LineBreak />
                     <Run x:Uid="AboutDialog_VersionLabel" />
                     <Run Text="{x:Bind ApplicationVersion}" />
                 </TextBlock>
+                <HyperlinkButton x:Uid="AboutDialog_SourceCodeLink"
+                                 NavigateUri="https://github.com/microsoft/terminal" />
                 <HyperlinkButton x:Uid="AboutDialog_DocumentationLink"
                                  NavigateUri="https://go.microsoft.com/fwlink/?linkid=2125416" />
                 <HyperlinkButton x:Uid="AboutDialog_ReleaseNotesLink"