feat: Declare a DevContainer for easy onboarding

[oliversalzburg]

DevContainers are a feature of VS Code: https://code.visualstudio.com/docs/remote/containers

They allow us to declare a development environment that is independent from the developers workstation. This allows us to easily work in a Node <12 environment, regardless of the Node version installed on the developers workstation.

PR Checklist

Please check that your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added or this is not a bug fix / enhancement
• Docs have been added, updated, or were not required

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[X] Other... Please describe: Developer feature

What is the current behavior?

AngularJS Material requires NodeJS <12 for development. Developers may already be using NodeJS 12+.

What is the new behavior?

Developers will get the ability to easily work on AngularJS Material in a defined environment, given that they meet the requirements to use the VS Code DevContainers feature.

Does this PR introduce a breaking change?

[ ] Yes
[X] No

[Splaktar]

I haven't heard of this feature of VSCode, but it seems useful.

We should probably support a full set of VS Code options/extensions similar to Angular and Angular Components.

However, we would need to add some Markdown documentation for both contributing with VS Code and separately, using the DevContainer.

For now, I'm going to target this at the 1.2.0 release where we will have a bit more flexibility for these types of changes.

[Splaktar]

We'll need to add a section about this in the developer guide found at docs/guides/BUILD.md.

[oliversalzburg]

@Splaktar That seems reasonable.

The last time I checked that guide, I got the impression that it was abandoned, because they mention gulp server, which isn't a valid gulp task.

Should I add a new section about DevContainer usage at the bottom and then maybe create a new ticket to review and correct the guide?

[oliversalzburg]

I added some documentaiton to the guide, although a lot of it is just describing the DevContainer feature in general. I tried to not duplicate too much. Users who use the extension or plan to use it, will likely educate themselves through the official documentation to an extent that they don't require a lot of introduction into the specifics in this project, as there are almost none.

I've also since added the default LiveReload port of gulp-connect to the forwarded ports, which now enabled the livereload feature as well when using the DevContainer.

[Splaktar]

The last time I checked that guide, I got the impression that it was abandoned, because they mention gulp server, which isn't a valid gulp task.

It's not abandoned and issues should be filed if it's not accurate. I've gone through and refreshed most of these, but this one does look like it needs a lot of attention. Thank you for the heads up.

Should I add a new section about DevContainer usage at the bottom and then maybe create a new ticket to review and correct the guide?

Yes, please.

[oliversalzburg]

I integrated a lot of the CircleCI stuff and cleaned it up. Full test suite can be run in the container now.