[js] TextMetrics.actualBoundingBoxLeft not available

[zommerfelds]

TextMetrics.hx does not have the latest fields defined in the API.

This might be because the latest WebIDLs refresh (#7354) was done in 2018.

Can we have the API updated?

@haxiomic are you planning to do this (saw you added yourself to similar issues like #10146).

If this is documented somewhere I can try to do it but it doesn't seem trivial.

[haxiomic]

It's planned – I'm aiming to move to using the IDL type definitions tool from the TypeScript compiler so we can have something easier to maintain. The current python script is layers of hacks and very difficult to maintain

For ETA, I'm expecting sometime this year; it's a sizable task whichever way we do it so it's hard to fit in