add c utf8 encoder / decoder
As discussed in #447 A C implementation for TextEncoder/TextDecoder, due to the limited access to the QuickJS internals it has some unnecessary overhead (basically encoding/decoding is done twice), but it is still much faster than in JS.
Some checks aren't succeeding due to #701
Merged the other PR, can you rebase?
All other tests are fine now. Not sure what macos is complaining about. Will look into that (maybe next week), though otherwise this is reviewable.
@saghul any updates here?
Sorry, I haven't had much time lately, I'll review this ASAP!