WEB: Added theme dependent favicon

[DeviousLab]

• closes WEB: Use appropriate favicon when user has browser in dark mode #42314
• tests added / passed
• Ensure all linting tests pass, see here for how to run them
• whatsnew entry

Added a light mode version of the favicon based upon the .svgs in the static folder as well as added a small js scipt to the template page to detect the theme change.

[attack68]

lgtm.

[jreback]

cc @datapythonista if any comment

[datapythonista]

Thanks for the contribution @DeviousLab. Looks fine, but I think we can get a way simpler implementation. Your code is only executed at load time, so why not leave the html as is (just adding an id), and the javascript simply have an if to check if the theme is dark, and if it change the href value?

[DeviousLab]

@datapythonista I probably have done it this way in the first place, but I've made the changes you've requested, now updates the favicon without requiring refresh through use of a event listener. And now just updates the href of the current favicon. Definitely a lot simpler.

[datapythonista]

I don't think a theme update is something we need to worry about, but in any case, this is much clearer, looks good to me.

Thanks for working on it @DeviousLab

[DeviousLab]

Are there any more changes that need to be made? Or can it be safely merged without conflicts?

[datapythonista]

Sorry for the delay @DeviousLab. We usually require two core devs to review a PR before merging, let's wait a bit more and see if someone else can have a look. Thanks for your patience.

[DeviousLab]

Sorry for the delay @DeviousLab. We usually require two core devs to review a PR before merging, let's wait a bit more and see if someone else can have a look. Thanks for your patience.

No worries! just thought I might have been missing something

[DeviousLab]

@jreback Does this look good to you?

[jreback]

thanks @DeviousLab