fix(30216): Add more docs for must version of functions

[DerekTBrown]

What does this PR do?

• Extend documents to address [Bug] regexFind doesn't panic as expected helm#30216 and Docs: Helm template function and "must" versions of functions #1020.

[TerryHowe]

I am not a maintainer, but there are some changes that need to happen here, thanks!

[TerryHowe]

There are links above and this change breaks that. I don't think you should change the headers or add the ### mustRegexMatch header here.

[TerryHowe]

Suggested change

	`regexMatch` will ignore regex compilation errors, and simply return `false` ([ref](https://github.com/Masterminds/sprig/blob/master/regex.go#L7))
	```
	{{- if regexMatch "[" "abc" -}}
	valid: true
	{{- end -}}
	```
	The above produces nothing.
	### mustRegexMatch
	Similar to `regexMatch`, but will return an error to the templating engine if the regex fails to compile:
	In the event of regex compilation errors, `regexMatch` will simply return `false`.
	Use `mustRegexMatch` to fail in the event of regex compilation errors.

[TerryHowe]

Suggested change

	### regexFind
	### regexFind, mustRegexFind

[TerryHowe]

I think these references are going to be brittle

Suggested change

	`regexFind` will result in a panic if the regex fails to compile ([ref](https://github.com/Masterminds/sprig/blob/master/regex.go#L30)), whereas
	`mustRegexFind` will return an error to the templating engine if the regex fails to compile ([ref](https://github.com/Masterminds/sprig/blob/master/regex.go#L34)).
	The `regexFind` function will result in a panic if the regex fails to compile, whereas
	`mustRegexFind` will return an error to the templating engine if the regex fails to compile.

[TerryHowe]

This project doesn't strictly use semantic line breaks, but I think it helps.

Suggested change

	Note that neither function will panic/return an error if the input string does not match the regex. Both functions return an empty string in this case:
	Note that neither function will panic/return an error if the input string does not match the regex.
	Both functions return an empty string in this case: