The official polybar documentation lives here.
The html documentation and man pages are built automatically when you build with cmake (cmake creates the custom
target doc).
The documentation uses Sphinx to generate the documentation, so you will need to have that installed.
If you build polybar normally while having Sphinx installed during configuration, the documentation will be enabled and
built as well. Building the documentation can be disabled by passing -DBUILD_DOC=OFF to cmake.
Once configured, all of the documentation can be generated with make doc or use make doc_html or make doc_man to
only generate the html documentation or the man pages respectively.
The HTML documentation is in doc/html/index.html in your build directory and the man pages are in doc/man.