Feat/fix select regex reveal

[SoraSuegami]

Description

This PR has the following three updates.

1. Fix the SelectRegexReveal template in circuits/utils/regex.circom to constrain that the given startIndex is less than maxArrayLen.
2. Add a note about an assumption that there should be only one consecutive sequence of non-zero bytes in in given to the SelectRegexReveal template.
3. Add new tests for the SelectRegexReveal template to circuits/tests/select-regex-reveal.test.ts.

Type of Change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

Checklist:

• I have discussed with the team prior to submitting this PR
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes

[saleel]

@SoraSuegami Isn't this check already enforced in VarShiftLeft - https://github.com/zkemail/zk-email-verify/blob/main/packages/circuits/utils/array.circom#L121-L122 ?

(Num2Bits will fail if out of bounds)

[saleel]

@SoraSuegami ^ Ignore above comment. I think we need both (bit range check and less thank check).

[SoraSuegami]

Thank you for your review!