Implement text outlines for UIElements

[ThunderEdge73]

Implements text outlines for UIElements. Partially addresses [#1446], as this PR does not cover outlines for DynaText objects. Set text_outline = colour in the config table of a UI node, where colour is a valid colour table, to add an outline to the given text node.

Additionally, in localization, use O:loc_colour to set the colour of the outline of description text. This text styling modifier will have no effect if the E: text styling modifier is present or if used within a name.

Additional Info:

• I didn't modify api's or I've made a PR to the wiki repo.
• I didn't modify api's or I've updated lsp definitions.
• I didn't make new lovely files or all new lovely files have appropriate priority.

[ThunderEdge73]

(also i do realize this is not the most performant way to do this, if anyone knows how to optimize this, please do)

[Aurelius7309]

The O: modifier will need a variable colour counterpart as well. Will need to look at what it can be

[Eremel]

The O: modifier will need a variable colour counterpart as well. Will need to look at what it can be

In that regard, underlining needs one too. Perhaps there could be a better way of doing it rather than just using an alternative key