gopls/doc: add instructions for the new "kokoro rerun" feature
gopls/doc: add instructions for the new "kokoro rerun" feature

Change-Id: Idb7ed8ab7f736cac10be1e9d5592e1ffb3f048eb
Reviewed-on: https://go-review.googlesource.com/c/tools/+/351090
Trust: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>
Run-TryBot: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>
Reviewed-by: Hyang-Ah Hana Kim <d7e82c3c07f92613bcbf9a1e88f6b96c13caa3b0@gmail.com>
gopls-CI: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools