Chore: Diamond performance optimization

[stas-kh]

What's been done:

1. Getting rid of redundant packages, CSS files, depenedencies
2. Adding webpack-bundle-analyzer
3. Optimizing lodash imports
4. Moving <app-page> outside of the router-outlet to reduce code duplications
5. Getting rid of unused components
6. Introducing sizes on simple-center-loader and making it CSS only (prevents sticking of the loader when feed is loading)
7. Removing bootstrap date picker in favor of pure HTML one
8. Getting rid of sprintf function and using built-in string literals
9. Making blog posts a separate lazy-loaded module
10. Importing quill-mention on demand to reduce final bundle size
11. Refactored some of imports (using relative path like ../../path instead of src/app/path-to-file)
12. Fixing most of production build warnings

Screenshots:

Lighthouse report on the most highly loaded content (feed) before optimization

Lighthouse report on the most highly loaded content (feed) after optimization

Webpack bundle analyzer comparison (vendor size is 1.5Mb smaller now, + blog posts is a separate module)

Production build + gzipped (latest numbers):