Replace npm with yarn; add CI workflow to run TSC and tslint checks

[laurence-myers]

To avoid linting issue sneaking in, particularly in the backend/server code, I've added a GitHub Action workflow to run tsc and tslint on every push.

yarn behaves better across different execution environments. In particular, npm ci failed to run in a GitHub Action, due to fsevents being a required dependency (somehow).

Example CI check:

https://github.com/laurence-myers/Video-Hub-App/runs/3578230215?check_suite_focus=true

This PR is based on #698, and includes its changes.

[whyboris]

Thank you for the contribution! I'll give it a try on Mac and Windows to see how it goes.

I remember when yarn was really ahead of npm in many ways, but it has felt like npm has caught up in terms of speed and locking dependencies 🤔

I'm not opposed to merging this -- I'll try it out first 🙇

[laurence-myers]

Thank you for the contribution! I'll give it a try on Mac and Windows to see how it goes.

I remember when yarn was really ahead of npm in many ways, but it has felt like npm has caught up in terms of speed and locking dependencies 🤔

I'm not opposed to merging this -- I'll try it out first 🙇

Yep, I'd be happy to stick with npm, I just didn't know if it would be possible to fix the issue where package-lock.json lists fsevents as a required (transitive) dependency. Maybe using resolutions in package.json?

Plus, I noticed package-lock.json has a bunch of possibly invalid dependencies beginning with node_modules. I ran npm shrinkwrap, which gave a much smaller npm-shrinkwrap.json file.

If you look at the number of lines changed, this MR removes approx 30,000 lines. Maybe it's because npm-shrinkwrap.json is more thorough in how it lists dependencies, but maybe it's because there's unnecessary/invalid entries.