design/32437-try-builtin.md: formatting improvements, added FAQ entry
design/32437-try-builtin.md: formatting improvements, added FAQ entry

Change-Id: I35d25fff6ff6f414b3103f530c253afc60c82cf0
Reviewed-on: https://go-review.googlesource.com/c/proposal/+/180500
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/proposal,golang/proposal