Rewrite extension for Manifest V3, add test coverage

[Paperfeed]

## Summary

This pull request introduces a comprehensive rewrite of the browser extension to support Manifest V3. Significant updates include theming support, improved dictionary parsing, migration to WXT and pnpm, and the addition of TailwindCSS for improved styling. The project structure has been refactored, transitioning from a class-based approach to a functional paradigm, and the inclusion of a global store enhances communication between background and content scripts. 

Additional features include:
- A rebuilt popup, options page, and dictionary runtime.
- Enhanced options page controls with color pickers.
- Regression test coverage for extension flows.
- Improved keybinding handling and hovering interaction in the popup.

## Changes in this PR
- Migrates extension to Manifest V3.
- Rebuilds core components: popup, options page, and dictionary runtime.
- Introduces theming and TailwindCSS integration.
- Refactors the project into a functional programming design.
- Enhances project configuration with WXT 0.21 and pnpm for future deployment to firefox
- Expands test coverage and fixes minor bugs related to dictionary entry parsing and key handling.