Write a "cell index / table" generator for the documentation

[mithro]

It is very useful to have tables of the cells available in each library. This should be included in the Sphinx generated PDK documentation. The task here is to auto-generate these tables as either;

• part of the Sphinx generation directly, or
• As a standalone script in (python-skywater-pdk package) which generates rst files committed to the repository (like the generated verilog or image files).

This should be easily be done due to the library structure being based around each cell having its own directory and a definition.json file which describes the basic shape and features of the cell.

Here is an example from a spreadsheet I created;

Here is an example from the libresilicon Standard Cell Library Build Report;

Here is an example from this random document

Here is another example from a random thesis on creating standard cells

[mithro]

Example cell - https://foss-eda-tools.googlesource.com/skywater-pdk/libs/sky130_fd_sc_hd/+/refs/heads/master/cells/a2111o/

Definition file which contains a summary of the cell info - https://foss-eda-tools.googlesource.com/skywater-pdk/libs/sky130_fd_sc_hd/+/refs/heads/master/cells/a2111o/definition.json