Split up the build of `annotator` and `sidebar` tailwind CSS into
separate tasks so they can be built against distinct tailwind
configuration. This allows the definition of `content` globs that are
specific to each entry point, avoiding the inclusion of irrelevant
styles in output CSS.

The other standalone CSS entry points — highlights, pdfjs-overrides,
katex — can be built against any tailwind configuration as they do not
enable any tailwind layers (and thus do not include any tailwind
utility classes).