Update dependency @webcomponents/webcomponentsjs to ^2.8.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@webcomponents/webcomponentsjs (source)	^2.6.0 -> ^2.8.0

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Release Notes

webcomponents/polyfills (@​webcomponents/webcomponentsjs)

v2.8.0

Compare Source

• Update dependencies (#​542)
• Polyfill Element.toggleAttribute(). (#​541)

v2.7.0

Compare Source

• Polyfill addEventListener/removeEventListener event listener options,
  including {capture: boolean, once: boolean}.
  (#​469)
• Make webcomponents-loader.js compatible with the Trusted Types API
  (#​501)
• Remove an arrow function in webcomponents-loader.js.
  (#​507)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.30%. Comparing base (ad1b546) to head (3862cde).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1229   +/-   ##
=======================================
  Coverage   69.30%   69.30%           
=======================================
  Files          59       59           
  Lines        5082     5082           
  Branches     1069     1069           
=======================================
  Hits         3522     3522           
  Misses       1533     1533           
  Partials       27       27           

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