Add support for sax xml parser

[timokoessler]

https://www.npmjs.com/package/sax

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 97.93103% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
library/sources/Sax.ts	95.45%	3 Missing :warning:

:loudspeaker: Thoughts on this report? Let us know!

[bitterpanda63]

Is dependant on #389