Switch to esbuild

[firelizzard18]

Microsoft now recommends using esbuild instead of webpack, for various reasons, including performance: esbuild is considerably faster than webpack. According to a random benchmark I found, esbuild is almost two orders of magnitude faster than webpack. I would be happy to submit a CL.

[hyangah]

Good idea (most of all, eslint is written in go and has API for go :-P)
Contribution is greatly appreciated!

[gopherbot]

Change https://golang.org/cl/343791 mentions this issue: all: bundle with esbuild instead of webpack