Update contribution guide and issue/PR templates

CONTRIBUTING.md

@@ -1,3 +1,27 @@
+# Welcome!
+
+If you are here, it means you are interested in helping us out. A hearty welcome and thank you! There are many ways you can contribute to the ML.NET project:
+
+* Offer PR's to fix bugs or implement new features.
+* Give us feedback and bug reports regarding the software or the documentation.
+* Improve our examples, tutorials, and documentation.
+
+## Getting started:
+
+Please join the community on [gitter](https://gitter.im/dotnet). Also please make sure to take a look at the project [roadmap](ROADMAP.md).
+
+### Pull requests
+
+If you are new to GitHub [here](https://help.github.com/categories/collaborating-with-issues-and-pull-requests/) is a detailed help source on getting involved with development on GitHub.
+
+As a first time contributor, you will be invited to sign the Contributor License Agreement (CLA). Please follow the instructions of the dotnet foundation bot reviewer on your PR to sign the agreement indicating that you have appropriate rights to your contribution.
+
+Your pull request needs to reference a filed issue. Please fill in the template that is populated for the pull request. Only pull requests adressing small typos can have no issues associated with them.
+
+An ML.NET team member will be assigned to your pull request once the continuous integration checks have passed successfully.
+
+All commits in a pull request will be squashed to a single commit with the original creator as author.
+
 # Contributing
 
 See [Contributing](Documentation/project-docs/contributing.md) for information about coding styles, source structure, making pull requests, and more.

ISSUE_TEMPLATE.md

@@ -0,0 +1,14 @@
+### System information
+
+- **OS version/distro**:
+- **.NET Version (eg., dotnet --info)**: 
+
+### Issue
+
+- **What did you do?**
+- **What happened?**
+- **What did you expect?**
+
+### Source code / logs
+
+Please paste or attach the code or logs or traces that would be helpful to diagnose the issue you are reporting.

PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,9 @@
+We are excited to review your PR.
+
+So we can do the best job, please check:
+
+- [ ] There's a descriptive title that will make sense to other developers some time from now. 
+- [ ] There's associated issues. All PR's should have issue(s) associated - unless a trivial self-evident change such as fixing a typo. You can use the format `Fixes #nnnn` in your description to cause GitHub to automatically close the issue(s) when your PR is merged.
+- [ ] Your change description explains what the change does, why you chose your approach, and anything else that reviewers should know.
+- [ ] You have included any necessary tests in the same PR.
+