DOC: Add edit this page links

[echedey-ls]

Main changes:

1. Enable View source links via html theme options
   This adds the following button under the github dropdown in the top bar
   

2. A rework of shamelessly stolen pvlib documentation configuration link composition; some helpers are the same (get_source_base_url, get_linenos) but get_obj_module implementation is substituted by get_linkable_source_object, which handles functions with the same name as a submodule (this is the case for solposx, as many functions are in a file called the same as them; previous name resolution gave prioritised getting a submodule). make_github_url stays similar. I don't know how the copyright impacts these functions, so please, guide me in this aspect.

3. In addition to enabling View source links via the theme, I wanted to add that button to the right sidebar like in pvlib (I like that visibility, personally I find the plain GitHub button misleading - it usually just represents the repo link). This theme claims that we can make use of pydata-sphinx-theme options (src). So I did but it arranges each element in horizontally 😞 . So here it comes the relevant CSS to fix that too.
   This is how it renders now:
   

[AdamRJensen]

@echedey-ls This is really cool stuff, and certainly an improvement! However, adding custom CSS seems likely to be a headache down the road to maintain. Given the small size of this repo, I think it's better to live with the slightly less than ideal doc site given the lower maintenance burden.

[echedey-ls]

Perfect, no problem. It's always faster to revert changes than to propose them. I will roll back till the relevant sections in this week.