Mkdocs-encryptcontent-plugin

- Code sanitation.
- Introduce file name obfuscation (make it harder or impossible to guess f.ex. image file names).
- Intorduce page obfuscation (make it harder for search engines or crawlers to read certain pages, f. ex. site imprint).
- Calculate minimum entropy of all used passwords and output warning below 100 bits.
- Download and verify self-hosted cryptojs just once.
- Check plugin order and output warning if "search" is behind "encryptcontent".
- The search_index handling is now more bulletproof (inspired by mkdocs-exclude-search).
- Fixed bug related beautifulsoup 4.12 (no problems up to 4.11).

Introduce use_secret as meta tag to allow use of environment variable as password source.

allow external scripts in content to be reloaded
make material/search index handling work again (patch for "dynamically" search index decryption for mkdocs-material currentyl doesn't work with 9.x.x)

fix translation: move decryption_failure_message to html template

add option to provide translation strings if used with static i18n plugin

fix imcompatibilty with Python < 3.9, [issue41](https://github.com/unverbuggt/mkdocs-encryptcontent-plugin/issues/41)