Update layout.html file in sphinx to add top menubar to astropy docs - #4

cc @astrofrog

Thanks, @pllim! Appreciate it

Hi! I just found out some issues with my PR and need more time to debug. But any suggestions or ideas would be appreciated.

Looking at the changes, I think most of these are specific to the core package, so I think we should customize the layout template there, not in this theme package (which is used by many packages)

@astrofrog - good point, it's my bad to forget about the packages that use the template but are not coordinated packages (for those this could be useful, too I think).

Yup @astrofrog, no problems! It is my first time so I did not check carefully enough before opening this PR, will effect the changes in my astropy/astropy repo then. Cheers!

Reopened this PR to follow up as suggested in astropy/astropy#8440 (review).

Hi @astrofrog, I have added an astropy-custom-menu as a html_theme option to the astropy-sphinx-theme repo in my PR. So now, at least in principal, if I set html_theme = 'astropy-custom-menu' instead of the default html_theme = 'bootstrap-astropy' option, the desired changes in the menubar should be effected. Please advise if this is what you had in mind as well.

And give me a brief moment to undo the previous commits regarding the bootstrap-astropy theme...

Think I have cleaned up every unnecessary change made in this PR prior to the last commit. Please review and confirm. Thanks!

And just to make sure, if I have changed the stylesheet in the theme.conf file, then I no longer need to add the new theme CSS style sheet to the layout.html file? Is my understanding of this correct?

I think I have managed to add the proposed menubar by configuring the theme at the astropy/astropy repo without having to resort to change the theme here. Therefore, I am closing this PR.

Hi, I have reopened this PR, and have added in items in the top menubar that would only be on if the sphinx variable astropy_project_menubar is set to True, so that people can opt out say by setting it to False. The PR is ready for a review now, as I was able to use a version of it on an affiliated repo to check locally, and obtained the desired effects. For a screenshot please see the following:

You are welcome @astrofrog! Yes, the custom.css is supposed to replace bootstrap-astropy.css, that's why the significant overlapping between the two files. But I initiated wanted to check first before making the replacement final.

Replacement of bootstrap-astropy.css file completed.

In addition to the small comment above, can you also rebase this?

Yup, rebased and squashed all commits into one and resolved one conflict in the layout.html file.

@kakirastern - there was an issue with the rebase, and a residual merge commit, so I've rebased it again and pushed to your branch. I think this should then be good to go.

@kakirastern - the option couldn't currently be set from the conf.py file so I've fixed that up and also added a changelog entry and information in the README.

I've also removed the astropy_banner_96.png file which was incorrectly added to this PR.