Adapt/extend codespell config

[ruestefa]

Suggested changes/extensions to codespell config:

• Move ignores to file (default entries are up for debate, I just copied the file from my notes repo)
• Keep ignoring all-uppercase words (acronyms), but not all uppercase words
  • Catch typos at the beginning of sentences at the expense of the occasional false-positive given name
• Skip lines with codespell-ignore comment (e.g., # codespell-ignore in Bash, Python etc., <!-- codespell-ignore --> in Markdown etc.)
  • Workaround for missing native support
• Skip files with .codespell-ignore. in name
  • Alternative to hardcoding the file name in the config