feat(gatsby-plugin-typescript): add support for numeric separators

[lsanwick]

Description

Similar to #19302, TypeScript has supported numeric separators since v2.7. As they are a Stage 3 proposal, I believe it's reasonable to add them to the configuration here so that Gatsby TypeScript users aren't surprised when numeric separators don't compile.

[pvdz]

Lgtm. Thank you for your contribution :)

[gatsbot]

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