Add missing tables of contents to the doc

[Joseph-Edwards]

The following pages are missing a table of contents, and should have one added:

• (Bipartition helpers)[https://libsemigroups.github.io/libsemigroups_pybind11/data-structures/elements/bipart/bipart-helpers.html]
• (Blocks helpers)[https://libsemigroups.github.io/libsemigroups_pybind11/data-structures/elements/bipart/blocks-helpers.html]

There may be more, and I will add them to this list as I find them