Add algorithms page

[edwardchalstrey1]

• Closes [Documentation]: Move algorithm descriptions from CLI manual pages to separate page #658
• New page link

[edwardchalstrey1]

@tturocy @rahulsavani this is not ready for merge but it's at a point where you can comment, take a look at this new algorithms page and let me know your thoughts.

Edit: On second thoughts, I think this PR is ready, the key thing to focus on is whether my splitting of the descriptions from the CLI pages makes sense - in some cases e.g. gambit-enumpoly, I have left parts of the description that refer to command line flags on the CLI page, rather than moving along with the rest of the description to the new algorithms page.

Do we want a similar page for other algorithms than Nash (QRE, others?)

[tturocy]

My first reaction is that it does expose how many gaps there are in the documentation for explaining what these methods do. :). (Or maybe more to the point, it exposes that there is documentation in our gaps!!!!)

In the first instance I suppose one page with subsections/anchors seems the way to go. I would suggest our idea would be that we'd want to aim for descriptions that are no more than what would be one side of A4. For more details we would link to original papers or surveys (where appropriate) or other sources for more information (e.g. a Jupyter notebook). That would mean one HTML page would make sense I think.

[edwardchalstrey1]

@StephenPasteris

• Editing docs: https://gambitproject--682.org.readthedocs.build/en/682/developer.contributing.html#editing-this-documentation
• Nash page: https://gambitproject--682.org.readthedocs.build/en/682/algorithms.html