Improve and test JavaScript code

[jigarius]

Requirements

• Remove unnecessary/unused code
• [x] Use TypeScript
  • [x] Fix all typing issues
  • [x] Remove any types
• Use 3rd-party libraries where possible
• Organize code into separate files
  • [x] Logically organize T2RWidget and T2RRenderer
  • [x] Create model shapes
• [x] Add code linter
  • [x] Fix all linter errors
  • [x] Fix all linter warnings
• [x] Add unit tests
• ~Add integration tests?~
  • To be tackled in a separate PR.
• Update GitHub Actions
  • [x] Lint JS code
  • [x] Test JS code

[jigarius]

This task turned out to be bigger than I had thought 😓 But it's a very good refactoring exercise. Here's what's left:

• Some more cleanup and organization
• Avoid having any types as far as possible
• Write unit tests where applicable
• Write integration tests where applicable?
• Test the UI with some realistic data
• Perform browser tests with popular browsers?
  • Maybe include Babel in the workflow? Not sure if the module JS work well with all browsers.

[jigarius]

Finally! The heavy-lifting is done! Everything has a type now 🥳 .

Here's what's left:

• [x] Resolve cyclic dependencies.
  • Dependencies between the objects are not clear at the moment, so they must be identified and established.
• [x] Rename rounding direction to rounding method.
• [x] Rename toggl workspace to toggl workspace id
• [x] Rename default activity to default activity id
• [x] Rename GET parameter workspaces to workspaceId
• [ ] More tests
• [ ] Minify compiled JavaScript?
• Clean up, wrap up, and merge!