Methods and Properties have no styled headings, making them inconsistent with classes/functions and unfriendly UX

[javabster]

I was taking a look at some of our documentation pages for Classes, Methods, Functions and Properties and I found some styling inconsistencies:

• Classes have styled headings with grey boxes, centred text, and a purple line on top
• Functions have styled headings with grey boxes, left aligned text, and a purple line on the left
• Methods have no styled headings
• Properties have no styled headings

Originally I wanted to open a PR here and to the qiskit_sphinx_theme to add styles to methods and properties headings, but now that i see there are different heading styles for Classes and Functions I'm not sure which style I should be following. My preference would probably be to have the heading styles for methods and properties match the styles for functions, but if anyone feels differently please let me know. Another option is we could change the class or function styles to follow a single style and enforce that for all page types? Just wanted to get some thoughts here before I open a bunch more PRs

You can see the difference between Classes and Functions below:

And methods are lacking any styles as you can see here:

[javabster]

closing as duplication of Qiskit/qiskit_sphinx_theme#45