Added tab related APIs - without functionality implemented yet

[jbicker]

What it does

It adds tab related APIs. For now it just solves the problem that we get an error when an extension uses the VSCode Tab API.
Functionality is not implemented on theia side yet.

How to test

1. Download this test extension:
   tab-test-0.0.1.zip
   and change the file type from zip to vsix
   or create it here
   or use another extension which uses the VSCode Tab API
2. install it in theia
3. trigger the command 'Close Active Tab'
4. see that nothing happens, even no errors notified anymore

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[paulalexwilson]

https://github.com/jbicker/tab-api-test-extension is not accessible to me

[JonasHelming]

This is great! Would you mind marking the members in theia.d.ts as @stubbed (see here for an example. This way, the stubbed members are showsn correctly as stubbed in the compat report (see here)

[jbicker]

@paulalexwilson, sorry about that. Try again!

[jbicker]

I squashed and force pushed with @stubbed markers.

[JonasHelming]

@rschnekenbu Could you run the VS Code compat checker over this branch and see whether all members are shown as stubbed (or supported)?

[rschnekenbu]

@JonasHelming, sure, I will run the tool tomorrow and give the result here

[rschnekenbu]

All members related to 'Tab' API are shown as @stubbed or implemented in @jbicker branch. That looks good to me on that aspect.

report: status.zip