[Feature Request] Get theme styles

Context

• This issue is not a bug report. (please use a different template for reporting a bug)
• This issue is not a duplicate of an existing issue. (please use the search to find existing issues)

Description

It'd be very helpful to be able to get the css declarations for classes used in editor and by the various colorize functions, e.g.:

.mtk1 { color: #d4d4d4; }
.mtk2 { color: #1e1e1e; }
.mtk3 { color: #cc6666; }
.mtk4 { color: #9cdcfe; }
.mtk5 { color: #ce9178; }
.mtk6 { color: #b5cea8; }
.mtk7 { color: #608b4e; }
.mtk8 { color: #569cd6; }
.mtk9 { color: #dcdcdc; }
.mtk10 { color: #808080; }
.mtk11 { color: #7c9c7c; }
.mtk12 { color: #f44747; }
.mtk13 { color: #c586c0; }
.mtk14 { color: #a79873; }
.mtk15 { color: #dd6a6f; }
.mtk16 { color: #5bb498; }
.mtk17 { color: #909090; }
.mtk18 { color: #778899; }
.mtk19 { color: #ff00ff; }
.mtk20 { color: #b46695; }
.mtk21 { color: #ff0000; }
.mtk22 { color: #4f76ac; }
.mtk23 { color: #3dc9b0; }
.mtk24 { color: #74b0df; }
.mtk25 { color: #4864aa; }
.mtki { font-style: italic; }
.mtkb { font-weight: bold; }
.mtku { text-decoration: underline; text-underline-position: under; }
.mtks { text-decoration: line-through; }
.mtks.mtku { text-decoration: underline line-through; text-underline-position: under; }

Motivation: We use monaco's colorize functions in a couple places on Compiler Explorer.

Monaco Editor Playground Link

No response

Monaco Editor Playground Code

No response

Start by tracing Monaco Editor's colorize functions and the CSS classes they use, including the .mtk declarations shown in the issue. Determine the API shape needed to expose those declarations and define completion against the Compiler Explorer use case described.