Ignore -postfix parameter to PackEachExperiment if prerelease tag is …

…not specified

This should hopefully be all we need for our release build

Updates build.yml trigger to automatically start workflow when a rele…

…ase branch is created

Icon updates and md cleanup (CommunityToolkit#158)

* First pass

* Fix xaml

* Adding more icons

* XAML styler

* More icons

* Adding shadow icon

* Minor sample tweak

* Update tooling

* Revert "Update tooling"

This reverts commit e653319.

* Update tooling

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Co-authored-by: Arlo <arlo.godfrey@outlook.com>
Co-authored-by: Michael Hawker MSFT (XAML Llama) <24302614+michael-hawker@users.noreply.github.com>