Implement String.prototype.codePointAt

[jasonwilliams]

ECMASCript feature
Implement String.prototype.codePointAt

MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/codePointAt
Spec: https://tc39.es/ecma262/#sec-string.prototype.codepointat

This code should now work and give the expected result:

onst icons = '☃★♲';

console.log(icons.codePointAt(1));
// expected output: "9733"

It will be similar to our implementation of charCodeAt

Contributing: https://github.com/boa-dev/boa/blob/master/CONTRIBUTING.md
Debugging: https://github.com/boa-dev/boa/blob/master/docs/debugging.md

[andylim0221]

I would like to take up this issue.

[Razican]

I would like to take up this issue.

Go ahead! :)

[croraf]

@andylim0221 Hi Andy. Any progress on this? Do you need some help?

[devinus]

Hope I'm not stepping on any toes, but I implemented this in #935 as a learning exercise.