Add feature for text detection API

[ddbeck]

Specification

Accelerated Text Detection in Images

This appears to be a companion to the Accelerated Shape Detection in Images specification.

Description

I discovered this feature via #3494 and https://chromium-review.googlesource.com/c/chromium/src/+/7077130, which are both pretty thin. This is my best guess based on reading the spec:

The TextDetector API locates text in images and converts it to text. Also known as optical character recognition.

Documentation

The spec's links to examples are busted. Presumably, someday there ought to be something in https://github.com/WICG/shape-detection-api.

• https://paul.kinlan.me/detecting-text-in-an-image/
• https://developer.chrome.com/docs/capabilities/shape-detection#textdetector

Browser support

• https://chromestatus.com/feature/5644087665360896
• https://issues.chromium.org/issues/40685969
• https://chromium-review.googlesource.com/c/chromium/src/+/7077130