cleanup docs

[nabe98]

Before submitting, please check the following:

• Make sure you have tests for the new code and that test passes (run tox)
• format added code by black -l 120 <filename>
• If applicable, add a line to the [unreleased] part of CHANGELOG.md, following keep-a-changelog.

Then, please fill in below:

Context (if applicable): cleanup and fix styles for docs

Description of the change:

Related issue:

also see that checks (github actions) pass. If lint check keeps failing, try installing black==22.8.0 as behavior seems to vary across versions.

[shinich1]

@nabe98 actually - I found that figs in tutorial got distorted. could you fix it too in this PR? https://graphix.readthedocs.io/en/latest/tutorial.html https://graphix.readthedocs.io/en/latest/intro.html https://graphix.readthedocs.io/en/latest/lc-mbqc.html

[nabe98]

Thanks for your review! I'll fix them in the next working time (maybe tonight or tomorrow night).

[shinich1]

@nabe98 great, the rendered doc is looking nice! please squash and merge.