fix(isBase64): simplify padding RegExp to prevent stack overflow

[KrayzeeKev]

Solves #2491 and #2573
Separate length check and then simplify regex to match any number of valid characters and 0 to 2 = on the end. Length check will ensure the {4} grouping is no longer necessary.

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (abcc8ec) to head (12211ff).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2574   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          114       114           
  Lines         2535      2536    +1     
  Branches       641       642    +1     
=========================================
+ Hits          2535      2536    +1     

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[KrayzeeKev]

Who is able to provide additional approvals and get this published? We've got production issues as a result of this. Need to decide whether we downgrade or hold out.

[andreasvh-conceto]

Also here with same issue on production. Currently using in nestjs class-validator library, which depends on this library. This a big problem for some partners, which send large documents. Here is an example:
example_fail.pdf
base64.txt

[WikiRik]

@rubiin are you able to review this soon? After merging this I want to get another release out

[andreasvh-conceto]

Thanks for your effort resolving this issue. Hope it gets released soon 🙏