tsconfig: update to target es2022

[hyangah]

During the review of https://go.dev/cls/606695

@firelizzard18 pointed out:

For reference, this repository lists each vscode version and what version of electron it uses and what version of node that uses: https://github.com/ewanharris/vscode-versions. And this website lists which ES20xx features are supported by which versions of node: https://node.green/. vscode-go currently supports vscode 1.75.0 and earlier, which means it must be able to support node 16.14.2 and later.

node.green shows that 16.14.2 supports almost the entirety of ES2018 (it's only missing escapes for unicode 14+), so we're good there.

It appears that 16.14.2 also supports up through ES2022 (except for one new RegExp flag does not appear in the flags property). So maybe we should update to ES2022 instead?

I think that's a valid point.
https://compat-table.github.io/compat-table/es2016plus/ also shows mostly green for recent versions of major browsers too.

[gopherbot]

Change https://go.dev/cl/606695 mentions this issue: extension/tsconfig.json: target es2022