Add `%` to autoclosing pairs

[juliasilge]

The Quarto extension provides a number of autoclosing pairs:

quarto/apps/vscode/language-configuration.json

Line 13 in 591b352

"autoClosingPairs": [

In posit-dev/positron#11110, we have @tomasrei requesting that we add % to that list, for uses in R like %in%. We do that in .R files in Positron like so:

https://github.com/posit-dev/positron/blob/d5962bb78f34e9db91be1002729bf752fddcb8aa/extensions/positron-r/language-configuration/r-language-configuration.json#L17

I think the main thing to consider is how disruptive this would be to non-R Quarto users.