Add CONTRIBUTING.md and ARCHITECTURE.md

[kevinramharak]

Fixes #159 (and #78).

Adds the following documentation:

• CONTRIBUTING.md
• ARCHITECTURE.md

This should lower the barrier of contributing to this repository and hopefully allow people to contribute to not only the source code, but also the open issues and discussion.

DRAFT:
So far I drafted the contributing guide from https://contributing.md/, and some online examples. I also wrote down the things in my head that are probably useful when developing the project. Feel free to add suggestions and changes.

Remaining things to add:

• write up ARCHITECTURE.md
• add instructions to build and locally install .vsix files
• add instructions how to create a new VS Code profile, to make it easier to choose what extensions are installed when debugging

[MichaelDimmitt]

My comment seems like a lot but it really is just asking what npm run dev does for the various apps in the mono repo.

[yoavbls]

Hey, is it ready for review and merge?

[kevinramharak]

Hey, is it ready for review and merge

Not yet, just a few more things to write up and add Michael's suggestions

[kevinramharak]

@yoavbls @MichaelDimmitt I'm just finishing this up for now. ARCHITECTURE.md could be filled in more and I still want to add something to explain the profiles, because its a usefull debugging tip, but for now this has been open long enough. I will create seperate issues for those to fill it in more. This should be enough of an improvement to give people some guidance when checking out the project.

[MichaelDimmitt]

Looks good thanks for adding this!