Improve tutorial and example overviews

[btjanaka]

Description

Various updates to tutorials to fit the new release of pyribs. This PR reframes the tutorials and examples, and there will be several followup PRs to implement and smooth out all the tutorials.

TODO

• [x] Start lunar lander CMA-MAE and DQD tutorial
• [x] Edit tutorials home page
• [x] Edit examples home page
• [x] Tweak original lunar lander tutorial to reflect CMA-MAE -> see #292

Questions

Status

• [x] I have read the guidelines in CONTRIBUTING.md
• [x] I have formatted my code using yapf
• [x] I have tested my code by running pytest
• [x] I have linted my code with pylint
• [x] I have added a one-line description of my change to the changelog in HISTORY.md
• [x] This PR is ready to go