Added integration with VSCode remote containers

[hugoabernier]

This PR adds a .devcontainer folder within the cli to allow contributors/consumers to open the solution in VSCode and automatically open within Docker (see Developing inside a Container); if you have the VSCode Remote Development extension pack and Docker installed, it'll ask you if you'd like to re-open the folder in a remote container. If not, it will assume you want to work locally.

Also made a minor tweak to .gitattribute file to avoid GitHub detecting every file as a change when opening solution within a container. It should help facilitate contributions and should keep the PRs cleaner.

Fixes #2072

[mikefactorial]

Thanks @hugoabernier this is fantastic! Would you mind opening an issue to relate this PR back to for traceability? https://github.com/microsoft/coe-starter-kit/issues/new?assignees=&labels=alm-accelerator%2Cenhancement&template=4-alm-accelerator-feature.yml&title=%5BALM+Accelerator+-+Feature%5D%3A+FEATURE+TITLE

[hugoabernier]

Thanks @hugoabernier this is fantastic! Would you mind opening an issue to relate this PR back to for traceability? https://github.com/microsoft/coe-starter-kit/issues/new?assignees=&labels=alm-accelerator%2Cenhancement&template=4-alm-accelerator-feature.yml&title=%5BALM+Accelerator+-+Feature%5D%3A+FEATURE+TITLE

Thank you! Added issue #2072

[mikefactorial]

Thanks @hugoabernier for taking the time to contribute and reiterating what @devkeydet said. It's great to have a community around this tool.