Remove usage of inline styles & inline scripts

[lb-]

It would good to remove our usage of inline styles and move these to the CSS or find a better way to achieve the same result.

This would allow projects to enable CSP for their docs if they want. It also aligns with the direction of Wagtail core - wagtail/wagtail#1288

theme files

sphinx-wagtail-theme/sphinx_wagtail_theme/extensions.html

Line 19 in ebfbb71

<label style="">Search for extensions by key:</label>

sphinx-wagtail-theme/docs/_templates/layout.html

Line 227 in ebfbb71

<div style="padding: 6px">

domainindex.html

I'm not sure what this file is for but maybe we need to check if we can change it or if it's used.

Note. We should really provide a better alt here also or just use alt="" if it's presentation only.

sphinx-wagtail-theme/sphinx_wagtail_theme/domainindex.html

Line 43 in ebfbb71

id="toggle-{{ groupid.next() }}" style="display: none" alt="-" />

Find a way to avoid inline scripts here. Maybe by setting this global in an existing JS file we already load.

sphinx-wagtail-theme/sphinx_wagtail_theme/domainindex.html

Lines 15 to 17 in ebfbb71

	<script>
	DOCUMENTATION_OPTIONS.COLLAPSE_INDEX = true;
	</script>

Originally posted by @ayaan-qadri in #304 (comment)

[ayaan-qadri]

I will work on this, I was planning to resolve it within that PR, but it would be messed up, I will raise different PR for this.

[ayaan-qadri]

@lb- I dig bit and found many times inline css is being used in wagtail:

https://github.com/search?q=repo%3Awagtail%2Fwagtail+%22style%22+language%3AHTML&type=code&p=1

If they are necessary to clean up for CSP, I would like to remove them all with proper test if the changes are not breaking anything (it will take long time).

[ayaan-qadri]

I'm not sure about the changes in domainindex.html, and the thing is that I could not find anywhere that it is being used.

[lb-]

@ayaan-qadri there's already a Wagtail (core) issue to cover CSP items, feel free to do an assessment / suggestion for changes on those issues. wagtail/wagtail#1288 & wagtail/wagtail#7053

As for this issue (the one in the Sphinx Wagtail theme), maybe let's just get a PR up that updates other usage and ignores the domainindex.html file for now.

Note that this work is low priority but smaller / focused PRs are welcome in this repo or the Wagtail one if you want to support these efforts.