Update esbuild to natively support Apple's M1

[marvinhagemeister]

This PR updates esbuild to the latest version which now includes a native binary for Apple's M1 chip. The speed improvement is quite noticable on my Macbook Air:

version	cold compile	watch change
0.8.45	4s	862ms
0.8.47	2.5s	649ms

Note: Every test file is compiled to a self contained bundle. We could even compile every test into one giant bundle to dramatically speed up things even further.

[coveralls]

Coverage remained the same at 99.445% when pulling a4eb33c on update-esbuild into b396932 on master.