Adopt the Xanadu Sphinx Theme

[Mandrenkov]

Context:
Currently, all Xanadu OSS projects include their own version of the Xanadu Sphinx theme; however, the Xanadu Sphinx Theme repository is now publicly available and is the preferred way to access the Xanadu CSS theme and Sphinx directives.

Description of the Change:

• Deleted the doc/xanadu_theme directory.
• Updated doc/requirements.txt and doc/conf.py to reference and use the (centralized) Xanadu Sphinx Theme.

Benefits:

• The size of this repository is smaller, meaning git clone will run faster.
• Updates to the Xanadu Sphinx theme no longer have to be manually ported to this repository.

Possible Drawbacks:
None.

Related GitHub Issues:
Depends on XanaduAI/xanadu-sphinx-theme#2.

Note to Reviewers:
The Install and Circuits pages capture most of the representative changes between the Sphinx themes.

[codecov]

Codecov Report

Merging #701 (b42fb35) into master (d00f4ed) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #701   +/-   ##
=======================================
  Coverage   98.72%   98.72%           
=======================================
  Files          75       75           
  Lines        9225     9225           
=======================================
  Hits         9107     9107           
  Misses        118      118           

Impacted Files	Coverage Δ
strawberryfields/apps/train/__init__.py	100.00% <ø> (ø)
strawberryfields/tdm/tdmprogram.py	99.19% <ø> (ø)

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[josh146]

❤️

A couple of things I noticed while browsing around:

• The logo and wordmark in the top left corner () should link to https://strawberryfields.ai. This is the first time I noticed this, since this is the first repo where the homepage != the docs homepage.

• In the master branch, autosummary tables are fullwidth, but this is not the case in the centralized theme.

[thisac]

Just a minor thing. I noticed the hover text isn't visible when on the edge (not sure how easy this would be to fix).

Also, a bummer that the font in the top left isn't "the Xanadu font" which was visible before when using an image instead.

[Mandrenkov]

Thanks for the review, @josh146!

• The logo and wordmark in the top left corner should link to https://strawberryfields.ai. This is the first time I noticed this, since this is the first repo where the homepage != the docs homepage.

Nice catch! 🎣 I've updated the theme to support custom href targets for the logo and wordmark in the navigation bar.

• In the master branch, autosummary tables are fullwidth, but this is not the case in the centralized theme.

Another great observation! 🔎 This has been fixed in the latest version of the centralized Xanadu Sphinx Theme.

[Mandrenkov]

Thanks, @thisac!

Just a minor thing. I noticed the hover text isn't visible when on the edge (not sure how easy this would be to fix).

Good eye! 👁 I don't think this would be too difficult to fix; however, I would prefer to just remove the tooltips as they (mostly) just repeat the title of the gallery item anyway.

Also, a bummer that the font in the top left isn't "the Xanadu font" which was visible before when using an image instead.

Yes, agreed, although I stand by the decision to use a consistent font across all of our OSS projects to ensure the Sphinx assets look crisp and unified. If only we had access to the Xanadu wordmark font...

[Mandrenkov]

As an update @thisac, after speaking with @josh146, I've restored the SF wordmark in the navigation bar.

[josh146]

Thanks @Mandrenkov!