[Housekeeping] Fix TSLint issues and upgrade dependencies

[stevehobbsdev]

• Fix tslint issues
• Update dependencies using npm update

TSLint issues ranged from:

• missing return types
• using angle-bracket type conversion syntax over as
• comment lines too long
• variable shadowing

This PR also adds a VSCode workspace file for recommending extensions for working on this project. Current recommendations include:

• TSLint
• Prettier

Additionally, it adds the npm run lint command to the CI build.

[stevehobbsdev]

@lbalmaceda This command just runs linting on the auth0-angular project.

What do you think about running this on the playground too in the future (i.e. all projects) by just using npm run lint? I think it would be a good idea. We could change it now but there are a few linting problems on the playground currently, so maybe something to add in once you've had a chance later to have a look at them. You can see the problems locally by running npm run lint.

[lbalmaceda]

Yes, I saw them as well. I think running this goes a bit along with the lgtm check (missing until we make the repo public).