Watchpage

- Added filter REMOVE LEFT
- Added filter REMOVE RIGHT

- Added Python 3.11 compatibility
- Added TRIM, LTRIM and RTRIM filters
- Added PREPEND and APPEND filters
- Added the REMOVE filter
- Added the REPLACE filter
- Added the REGEX SEARCH filter
- Added the REGEX REPLACE filter
- Added the REVERSE filter
- Added the UPPER and LOWER filters
- Added the JSON DICT filter
- Added the JSON LIST filter
- Added the LEFT and RIGHT filters
- Added type github-tags-zip and github-tags-tgz to parse GitHub tags in format .zip and tar.gz

- Replaced the html5 parser with html5lib
- Added special prefix github: to parse GitHub repositories
- Added type github-tags to parse GitHub tags
- Skip empty URLs

- Add request headers from configuration
- Added agent command line option to specify the default User-Agent

- Added icons
- Added some samples

- Code cleanup