Add 'typescript' alias extension for 'ts'

[thiagowfx]

Precedent: JavaScript has both 'javascript' and 'js', this ensures consistency.

(edit: there's no 'js', my mistake)

[asottile]

there's no js tag so there's no precedence

[thiagowfx]

Maybe my point was misunderstood. https://github.com/pre-commit/identify/blob/main/identify/extensions.py

What I meant was this:

Status quo:

• 'javascript' (no 'js' indeed as you say)
• 'ts' (no 'typescript')

With this PR, status quo:

• 'javascript'
• 'typescript'
• 'ts'

The rationale is: When using pre-commit with a kind filter, it has to be written like this: https://github.com/GoogleChromeLabs/chromium-bidi/blob/fc2d6847cc4c5dd10a46693055c7faa7827079f4/.pre-commit-config.yaml#L111

        types_or: [javascript, ts, python]

However, one would expect the following to be valid (but it's not!):

        types_or: [javascript, typescript, python]

...this PR intended to fix this inconsistency.

The precedence is for 'javascript'.

[asottile]

search the issue tracker -- this inconsistency has been discussed before with resolution as to why it is not changing