chore: add theme variable helper scripts

[jonas-jonas]

Related Issue or Design Document

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact [email protected]) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

Further comments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.56%. Comparing base (f3fad4d) to head (2870554).
Report is 30 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #341      +/-   ##
==========================================
+ Coverage   42.43%   50.56%   +8.13%     
==========================================
  Files         136      138       +2     
  Lines        2008     2106      +98     
  Branches      288      313      +25     
==========================================
+ Hits          852     1065     +213     
+ Misses       1149     1029     -120     
- Partials        7       12       +5     

Components	Coverage Δ
@ory/elements-react	47.33% <39.02%> (+10.54%)	⬆️
@ory/nextjs	64.33% <74.24%> (-1.65%)	⬇️