v1.0.0-prerelease.15

Changelog

• 5d6ca9e add meta viewport tag to pfe-content-set demo (#415)
• ee6fde4 adding a slotchange listener and adding tests (#407)
• bf8790f Card feature updates (#312)
• 5d1fa72 reset surface-border color to #d2d2d2
• e8260e5 PFE-accordion border fixes
• 84dbf03 Pfe docs status (#408)
• 827aa51 Update Storybook utils to support self-closing tag (#411)
• 393098c Rename PR template directory & file in hopes that github will use them (#410)