Use different logos for light and dark theme

[12rambau]

I refactored navbar-logo.html to support 3 different logo structures (2 logos, 1 logo, no logo). I made the following modifications:

find the link

As the same link will be used whatever the logo, I decided to set a variable at the begining of the file

2 logos

The user set the logos in the defined static folder and set the relative path in the options:

html_static_path = ["_static"]
html_theme_options = {
    "light_logo": "logo-light-mode.png",
    "dark_logo": "logo-dark-mode.png",
}

I then create 2 independant logos, one using only-dark the other only-light.

This option only works if both the logo are set

demo ?

As long as the theme documentation has not yet a logo (please have look in #373) I cannot really demo it here. you can either trust me (not recomended) or test it on one of your doc and let me know 😄

Fixes #674 fixes #545

[choldgraf]

Nice! A few quick ideas/comments from me but this is looking good!

[choldgraf]

This looks pretty good to me! A few quick suggestions on docs wording

[choldgraf]

this isn't necessary because html_title is built into Sphinx, I believe

[choldgraf]

Made a few small docs tweaks! This looks good to me! I am going to merge and try this out in #698 !

[12rambau]

I had not removed the html_title from conf 😄. I will clean it somewhere else

[choldgraf]

I removed it just before merge but reintroduced a version of it back into the branding update PR 🙂