refactor: react-app using hooks, hash-routes, lazy-loading, and upgraded deps

[emagnier]

A bit of ❤️ for this project, which also serves as a showcase on romcal.js.org:

• Lazy load calendar & locale data (for faster site loading).
• Removal of MobX, and the use of stores in general.
• Instead of stores, use the URL to store contextual information (calendar, locale, year, month), and React custom hooks (for retrieving and manipulate data).
• Install react-router-dom, and use a HashRouter. FYI, GitHub Pages (where is currently hosted romcal.js.org) doesn't support BrowserRouting and custom URLs (although there is a hack).
  
• Use hooks (less verbose than MobX, and simpler to use in React components) to access and manipulate contextual information (calendar, locale, year, month), navigate the liturgical calendar, and access romcal data (with the help or react-query, to manage the state of the data more easily).
• Update all dependencies, except eslint (eslint-config-airbnb doesn’t support eslint v9 yet).
• Some refactoring to improve the code (with related eslint rules):
  • Use the type keyword on imports when appropriate.
  • Generalize the use of named exports.