Make String#substr more discoverable

[sevenc-nanashi]

ECMASCript feature
Explain the ECMAScript feature that you'd like to see implemented.

String.prototype.substr (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr). It's deprecated, but it is still used in many libraries.

Example code
Give a code example that should work after the implementation of this feature.

const str = 'Mozilla';

console.log(str.substr(1, 2));
// Expected output: "oz"

console.log(str.substr(2));
// Expected output: "zilla"

[jedel1043]

Already implemented, just gated behind the annex-b feature.

boa_engine = { version = "0.18.0", features = ["annex-b"] }

[sevenc-nanashi]

Oh, thanks!

[jedel1043]

I'll keep this issue open though, since it seems that we need to have better discoverability for that specific feature; "annex-b" is not as well known for people without spec expertise.

[nekevss]

Maybe, we can add this as a page on the website? Something akin to feature flags, and the features that are behind each flag?