doc/go1.17: document text/template/parse.SkipFuncCheck
doc/go1.17: document text/template/parse.SkipFuncCheck

Documents the newly added mode that skips type checking
functions as per CL 301493.

Fixes #46025
For #34652
For #44513
For #38627

Change-Id: I56c4f65924702a931944796e39f43cfeb66abc8a
Reviewed-on: https://go-review.googlesource.com/c/go/+/311569
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Emmanuel Odeke <bd234ba4276433f0e5fc7a8fa2d18274fa711567@orijtech.com>
Trust: Michael Knyszek <4473450dc5c88f06e1fb787f303d7805ec2aee65@google.com>

golang/go,CAFxX/go,CAFxX/go,golang/go,golang/go,CAFxX/go,cloudflare/go,CAFxX/go,nawawi/go,nawawi/go,cloudflare/go,golang/go,golang/go,golang/go,CAFxX/go,nawawi/go,nawawi/go,cloudflare/go,nawawi/go,nawawi/go,cloudflare/go,nawawi/go,nawawi/go,cloudflare/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,CAFxX/go,golang/go,CAFxX/go,cloudflare/go