Add support for monospaced fonts with programming ligatures

[jrappen]

Add support for monospaced fonts with programming ligatures such as:

• https://github.com/tonsky/FiraCode
• https://github.com/i-tu/Hasklig

[FichteFoll]

Please refrain from cc'ing Jon, he will find his own way to these issues if he needs to. On another note, all issues have the same privileges (i.e. the same right to be seen) so only ccing some of them is unfair.

[jrappen]

Ligature support does not fit well with Sublime Texts current approach for text rendering. I'd like to see them working at some point, but it won't be soon.

[buildersbrewery]

Ligatures work in mdpopups 👍

/cc @facelessuser

[ConnahILE]

When is this due to be included in the build? Been waiting for ligatures for aaaaaggggeeeeesssss

[thatwasawkward]

Please add support for ligatures. Sublime is fantastic otherwise, but this seems like a pretty obvious improvement that's probably not worth losing users over?

[FichteFoll]

Of course it would be an improvement, but also not trivial because of internals that need to be rewritten and restructured. I'm certain it won't be coming before 3.0 stable.

Here's the latest official statement on font ligatures: https://forum.sublimetext.com/t/support-font-ligatures/17654/10?u=fichtefoll

It isn't exactly a matter of figuring something out as it is making significant architectural changes to how glyphs are cached and then drawn.

You can be fairly sure there won't be any changes to ligature support before 3.0 is released.