ci: Add weekly npm update to Dependabot

[Flash0ver]

Summary

Add weekly npm update to Dependabot,
as we're in the process of adding local npm tools,
for both dotagents and warden.

Remarks

Follow-up to:

• chore: update and pin dotagents #5026
• chore: add Warden #5024

No more hiding from JavaScript outside the Browser 😉

This is similar to #5005 ... but for npm

See docs: https://docs.github.com/en/code-security/reference/supply-chain-security/supported-ecosystems-and-repositories

[github-actions]

Semver Impact of This PR

⚪ None (no version bump detected)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.93%. Comparing base (bfe5319) to head (5e1dc39).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5028      +/-   ##
==========================================
+ Coverage   73.92%   73.93%   +0.01%     
==========================================
  Files         497      497              
  Lines       17974    17974              
  Branches     3517     3517              
==========================================
+ Hits        13287    13289       +2     
+ Misses       3832     3826       -6     
- Partials      855      859       +4     

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