Making a few improvements to the GitHub action which does a test bundle.

* Better docs/comments
* Better name
* Support "master" or "main" branch as new forks will use `main`
  * https://www.zdnet.com/article/github-to-replace-master-with-main-starting-next-month/
  * https://github.com/github/renaming
* Add both a ruby gem cache as well as an npm cache to speed things up (CLI install is most of the time spent currently)

Update Test Badge in README.md

Upload bundled .zip file on PRs for easy testing

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… links on PDP's page (bigcommerce#1809)

…right side when in focus (bigcommerce#1823)

…igcommerce#1813)

fix(storefront): BCTHEME-211 Cross icon on close button missalignment

…thin faceted search (bigcommerce#1815)

Co-authored-by: BC-tymurbiedukhin <66319629+BC-tymurbiedukhin@users.noreply.github.com>

fix(storefront): BCTHEME-191 Incorrect styles for focused buttons in grid card product item

…mmerce#1800)

Co-authored-by: BC-tymurbiedukhin <66319629+BC-tymurbiedukhin@users.noreply.github.com>

…ording to AA standard (bigcommerce#1804)

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… View (bigcommerce#1799)

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…rd (bigcommerce#1814)

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… color (bigcommerce#1817)

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…ng (bigcommerce#1828)

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…fo button (bigcommerce#1844)

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…earch (bigcommerce#1826)

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…bigcommerce#1835)

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…ce#1829)

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…ce#1837)

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… since not needed (bigcommerce#2018)

…ns PDP (bigcommerce#2023)

fix(search): ES-2138 fixed count showing issue for category facet

…ommerce#2029)

…new global region for html widget (bigcommerce#2026)

bigcommerce#2028)

…ge carousel image (bigcommerce#2027)

…uct page (bigcommerce#2001)

…P Pages (bigcommerce#2022)

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…sels (bigcommerce#2034)

fix(storefront): DEV-426 Fix GitHub workflows for default storefront

…fixed (bigcommerce#2043)

…achieve accessibility AA Complaince (bigcommerce#2047)

…d by screen reader (bigcommerce#2024)

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