Refactor: Improve install instructions

Updated installation instructions with a new banner and refined configuration details.  The banner now includes the Sublime Text logo and highlights the plugin's purpose more clearly. Configuration instructions now explicitly mention the need to replace placeholder usernames and passwords with actual credentials.

messages/install.txt

@@ -1,20 +1,30 @@
-Sublime Text 3/4 plugin for Simplenote. Use Sublime Text as a Simplenote client.
+Sublime Text 3/4 plugin for Simplenote
+========================
+Use Sublime Text as a Simplenote client.
+--------
+     _                 _                  _
+ ___(_)_ __ ___  _ __ | | ___ _ __   ___ | |_ ___
+/ __| | '_ ` _ \| '_ \| |/ _ \ '_ \ / _ \| __/ _ \
+\__ \ | | | | | | |_) | |  __/ | | | (_) | ||  __/
+|___/_|_| |_| |_| .__/|_|\___|_| |_|\___/ \__\___| for Sublime Text
+                |_|
+--------
 
 First time use, To configure your Simplenote account username and password in the settings file, follow these general steps:
 
 1. **Open the Settings File:**: Sublime Text > Settings > Package Control > Simplenote > Settings
 
 2. **Configure Username and Password**
    - Look for the configuration section and add or modify your username and password. For example, if the configuration file is in JSON format, you might add the following content:
-     ```json
+     ```
      {
-       "username": "your_username",
-       "password": "your_password"
+       "username": "your_simplenote_username",
+       "password": "your_simplenote_password"
      }
      ```
-   - Make sure to replace "your_username" and "your_password" with your actual username and password.
+   - Make sure to replace "your_simplenote_username" and "your_simplenote_password" with your actual username and password.
 
 3. **Save the File**
 
-5. **Restart the Application**
+4. **Restart the Application**
    - Sometimes you need to restart Simplenote or the related application for the new settings to take effect.