client: update documentation
client: update documentation

The documentation is updated to add relevant links and fix typos.

The TODO is moved to https://go.dev/issue/53224.

Change-Id: I2e68312ca4a2ea39a9108d5b43544ac955b902d3
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/410174
Reviewed-by: Zvonimir Pavlinovic <490af24f3def1258d2f7e9b10b20e341f6c68320@google.com>
Reviewed-by: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>

golang/vuln,golang/vuln