gh-pages fails to build after commit 8897f7e; MANUAL.md: invalid byte sequence in UTF-8

[tekenstam]

It seems that after commit 8897f7e the GitHub Pages build started failing. If I try to do jekyll build of HEAD of master I see the following:

$ jekyll build
Configuration file: none
            Source: /Users/tekenstam/src/yoda-2/docs
       Destination: /Users/tekenstam/src/yoda-2/docs/_site
 Incremental build: disabled. Enable with --incremental
      Generating...
Error reading file /Users/tekenstam/src/yoda-2/docs/MANUAL.md: invalid byte sequence in UTF-8
  Conversion error: Jekyll::Converters::Markdown encountered an error while converting 'MANUAL.md':
                    The source text contains invalid characters for the used encoding UTF-8
                    ------------------------------------------------
      Jekyll 4.1.0   Please append `--trace` to the `build` command
                     for any additional information or backtrace.
                    ------------------------------------------------

If I checkout commit 8897f7e8066b89f280b92a966537fd1f6464066b then jekyll build works.

$ git checkout 8897f7e8066b89f280b92a966537fd1f6464066b
:
:
$ jekyll build
Configuration file: none
            Source: /Users/tekenstam/src/yoda-GitHub/docs
       Destination: /Users/tekenstam/src/yoda-GitHub/docs/_site
 Incremental build: disabled. Enable with --incremental
      Generating...
                    done in 0.451 seconds.
 Auto-regeneration: disabled. Use --watch to enable.