Doc CSS improvement

The last column is cut-off:

If we increase [--content-max-width](https://github.com/bazel-contrib/rules_foreign_cc/blob/568a37e797e7be7e497b30c057e1e2b913647ad1/css/variables.css#L9) it looks much nicer:

Or maybe we can just remove `--content-max-width` so that it can automatically adjust the width?

Start by inspecting css/variables.css, especially --content-max-width, and compare the documented layout shown in the issue. Determine whether increasing or removing the constraint keeps the documentation content readable while showing the last column. Done means the affected documentation view no longer cuts off that column.

Written by the indexing model from the issue text.