Render math in R completion popups and help

[kevinushey]

For example, the help for rnorm as viewed in RStudio:

VSCode appears to only accept Markdown and plain text by default, though. Here's that that looks like with a naive HTML-to-Markdown implementation with Pandoc.

[kevinushey]

See also: https://github.com/rstudio/positron/blob/adef2daca20e07e3e757ffa06730979505abd7f5/src/vscode-dts/vscode.d.ts#L4165-L4169

[kevinushey]

Alternatively, we can limit the amount of help we show in the completion popups to a smaller subset and just let a separate Help pane manage the display of arbitrary help HTML.

[kevinushey]

Here's how things look currently:

This is probably good enough for MVP, but I think we'll eventually want a way to make sure that we render latex / MathJax appropriately.

[Fred-Wu]

Would this be made to Python too? For example , in torch, it currently shows:

[juliasilge]

@Fred-Wu I believe the Python support is tracked in #1522, if you'd care to add details or an example there.