Add GitHub templates

[bollwyvl]

Just to get the ball rolling...

References

#96

Code changes

N/A

User-facing changes

Contributors/end users will see a little more UI when making PRs/Issues: https://help.github.com/en/github/building-a-strong-community/about-issue-and-pull-request-templates

Backwards-incompatible changes

N/A

Chores

• linted
• tested
• documented
• changelog entry

[jupyterlab-dev-mode]

Thanks for making a pull request to JupyterLab!

To try out this branch on binder, follow this link:

[bollwyvl]

Great: this demonstrated the flake on win/py37, and it was corrected in the third run. The test failures are still captured in the test results:
https://dev.azure.com/krassowskimichal/jupyterlab-lsp/_build/results?buildId=155&view=ms.vss-test-web.build-test-results-tab

and the robot logs have a (relatively) clear representation of what flaked:

The overall runtime was 33min, which is better than 40min if we re-kicked the whole thing, and certainly better, since we didn't have to do anything manually.

[krassowski]

Thank you, the templates are great!