Add strict css module checks

[matt-gadd]

Type: feature

The following has been addressed in the PR:

• All code has been formatted with prettier
• Unit or Functional tests are included in the PR

Description:
This throws warnings in the build if we detect any selectors in m.css files that can potentially leak into other widgets. The 2 scenario's handled with this PR are any element/tag selectors and the universal selector.

[tomdye]

Gona cause a lot of hurt, but it's for the best!
Should probably raise for build-widget / build-theme etc too.
Nice 👍

[codecov]

Codecov Report

Merging #251 into master will decrease coverage by 0.01%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##           master     #251      +/-   ##
==========================================
- Coverage   52.48%   52.46%   -0.02%     
==========================================
  Files          10       10              
  Lines         625      629       +4     
  Branches      157      157              
==========================================
+ Hits          328      330       +2     
- Misses        297      299       +2

Impacted Files	Coverage Δ
src/base.config.ts	23.75% <50%> (+0.59%)	⬆️

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