Implement ViewIt Plugin System Documentation and Update Project Notes

- Added comprehensive documentation for the ViewIt Plugin System, detailing the plugin loading process, required methods, optional features, and community extension workflow.
- Updated project notes to reflect the current structure, build process, search logic, and known issues.
- Introduced new build scripts for installing the add-on and creating ZIP packages.
- Added test scripts for TMDB API integration, including argument parsing and logging functionality.
- Enhanced existing plugins with improved search logic and error handling.

dist/plugin.video.viewit/regex_patterns.py

@@ -0,0 +1,11 @@
+#!/usr/bin/env python3
+"""Shared regex pattern constants.
+
+Keep common patterns in one place to avoid accidental double-escaping (e.g. \"\\\\d\").
+"""
+
+SEASON_EPISODE_TAG = r"S\s*(\d+)\s*E\s*(\d+)"
+SEASON_EPISODE_URL = r"/staffel-(\d+)/episode-(\d+)"
+STAFFEL_NUM_IN_URL = r"/staffel-(\d+)"
+DIGITS = r"(\d+)"
+