Allow double dollar signs for interpolated strings as in C# 11

[abonie]

Is your feature request related to a problem? Please describe.

This issue is for tracking work on this feature suggestion fsharp/fslang-suggestions#1150 that is "approved-in-principle"

It is meant for improving the experience of embedding another language (or JSON data) in F#

Describe the solution you'd like

Based on design principle from FS-1001-StringInterpolation:

Support the same syntax, use cases and technical features as C# interpolated strings.

I'd like to have same support in F# for multiple $ signs prefixing interpolated string to affect how curly braces within that string are escaped.

RFC here: FS-1132

Describe alternatives you've considered

Not doing it

[abonie]

Update: related RFC is merged now, see here