Use Menlo instead of Monaco in generated documentation

[slice]

Details/Motivation

Monaco is specified second to last in the font stack, but is never used because macOS has the Courier New and Courier fonts, which always gets used instead and looks pretty bad.

This patch adds Menlo to the front of the font stack and moves Monaco to be after it.

This shouldn't affect font displays on platforms other than macOS.

Comparison

Before:

After:

[straight-shoota]

What's the reason for using Menlo?

[j8r]

People finds the Menlo font more readable than Courier fonts @straight-shoota . Not a big deal, but quite agree.

[straight-shoota]

I don't think this improves anything by itself. We should have an extensive concept for design improvements to the API docs.

There is already an issue to discuss fonts (#5053). I'd propose to continue this topic over there instead of an isolated PR.

However, I also think that redesigning the API docs should come after a proposed refactoring of the docs generator, which would separate it from the compiler and only transform JSON data to HTML (and other target formats). But at the moment there are certainly more important things to do and IMHO it would probably best to postpone this.

At least I don't see a pressing urgency to replace Consolas, Courier, Monaco with Menlo, Consolas, Courier (it doesn't hurt either, though).

[refi64]

I mean, it really doesn't hurt to fix this, since it seems there's at least a few people who like this.

[slice]

While this isn't any kind of long term solution, I figured it would be a nice short term improvement to the look of the docs. 😄

[bcardiff]

I love fonts. There is a long term design pending story. Actually we do have a nice design but never implemented. The community built the current one, but we do expect to match the general style of the homepage some day.

That been said, the font ordering that this PR propose make sense.
Thanks @slice !