Opinionated styling, package and code updates

[TheLartians]

Hey, thanks for this great template! It really helped me get started with Chrome extensions. Doing so, I've made a few adjustments to the starter that make it much more usable for me. I was wondering if some of these changes could be interesting for the original template as well.

I know that these are very opinionated changes, so feel free to simply ignore/close the PR if you are not interested. I could also split anything you find interesting into separate PRs, if you prefer.

Summary of changes

• Switch from npm to yarn
• Switch from jQuery to React
• Add auto reload capability (should also address content_script not updating #18)
• Add prettier to enforce code styling
• Remove the moment package in favour of the JS's built-in Date class
• Switch from Travis CI to GitHub Workflows
• Run tests and check style in CI
• Inline the example sum.ts file into the example test, as it's not used for anything else
• Enable strict mode and allow compiling with errors (TS correctness will be checked in CI)
• Remove polling background script to prevent accidental console spamming
• Add a new svg logo for the project, from which the extension icons are automatically generated in 128px, 48px and 16px resolution
• Update the Readme to feature the new logo
• Remove .vscode/tasks.json as vscode will automatically detect tasks from package.json

[chibat]

Thanks for your PR.
I will refer to it and try to incorporate it partially.

[LazyCompiler]

Very useful change!
A worth mentioning thing is that the script "prepare": "./prepare_icons.sh" use the command convert which is part of ImageMagick, so make sure you guys install it before (brew install imagemagick).

[chibat]

@TheLartians
I would be grateful if you could create another new PR for the following changes.

• Switch from jQuery to React
• Remove the moment package in favour of the JS's built-in Date class

[TheLartians]

Sure, I'll create the new PR later today!