readme.md: add a section how to find the SIG (#4031)
readme.md: add a section how to find the SIG (#4031)

* readme.md: add a section how to find the SIG

* Update README.md
bazelbuild/intellij,bazelbuild/intellij,bazelbuild/intellij,bazelbuild/intellij,bazelbuild/intellij,bazelbuild/intellij,bazelbuild/intellij