Fixes RangeError in base64url.ts when encrypting large Uint8Arrays
String.fromCharCode.apply causes a RangeError for large Uint8Arrays
(> ~500kB). This happens, e.g., when encrypting larger files.
See this gist to reproduce the bug (select a large file and see the
browser console):
https://gist.github.com/codedust/88c8af3b2acd782e72ffbe0c3c8bf5af
Error message in Firefox:
```
Uncaught (in promise) RangeError: too many arguments provided for a
function call (in base64url.js:8:62)
encode http://localhost:8000/jose/runtime/base64url.js:8
encrypt http://localhost:8000/jose/jwe/flattened/encrypt.js:143
```
Error message in Chromium:
```
Uncaught (in promise) RangeError: Maximum call stack size exceeded
at encode (base64url.js:8)
at FlattenedEncrypt.encrypt (encrypt.js:143)
at async CompactEncrypt.encrypt (encrypt.js:23)
at async jwe_test ((index):55)
```
Solution: Apply String.fromCharCode.apply in chunks of 32768 bytes,
see https://stackoverflow.com/a/12713326
BREAKING CHANGE: Revised, Promise-based API
BREAKING CHANGE: No dependencies
BREAKING CHANGE: Browser support (using [Web Cryptography API](https://www.w3.org/TR/WebCryptoAPI/))
BREAKING CHANGE: Support for verification using a remote JWKS endpoint
BREAKING CHANGE: Experimental Node.js libuv thread pool based runtime (non-blocking 🎉)
