Adding Python f-string syntax support

[samstrohkorbatt]

Adding Python f-string support, as mentioned in issue: microsoft/monaco-languages#1762

This includes new tests for the f-string formatting, and all current string tests are passing, so these changes are isolated to only f-strings

[samstrohkorbatt]

@microsoft-github-policy-service agree [company="{AT&T}"]

[samstrohkorbatt]

@microsoft-github-policy-service agree company="AT&T"

[samstrohkorbatt]

Hi @hediet and @alexdima,
Would either of you two be able to review this PR? It's been open for 2 weeks without any feedback so far

Best,
Sam

[samstrohkorbatt]

Hi @rzhao271, @hediet, and @alexdima,
Could any of you review this PR? It's been open for 6 weeks now and no one has provided any feedback yet

Best,
Sam

[hediet]

Thanks for the PR! And sorry for the delay.