codespell: action, config and some typos fixed

[yarikoptic]

with this action no new typos should sneak in

[digint]

Thanks a bunch, I never got around to play around with github actions; codespell makes much sense here.

I changed the config to include the ignore-word-list, as I hate to have the source tree polluted with plenty of config files. Also I splitted the spelling fixes into multiple commits.

Commits:

• a4d4dff - btrbk_restore_raw.py: fix spelling
• d819f17 - kdf_pbkdf2.py: fix spelling
• 1807ad5 - btrbk-mail: fix spelling
• b139875 - btrbk: fix spelling
• f6bdab1 - documentation: fix spelling
• 16364e2 - documentation: remove obsolete upgrade_to_v0.23.0.md
• efa4d13 - ChangeLog: fix spelling
• dac6350 - github: actions: add codespell master on push and PRs

[yarikoptic]

coolio!