v0.30.4-ls111

LinuxServer Changes:

Rebase to alpine 3.12. Fix APP_URL setting. Bump php post max and upload max filesizes to 100MB by default.
bookstack Changes:

Security Release

• Update Instructions
• Vulnerability Reports:
  • Cross-Site Scripting and Redirects Through Page Content
  • Cross-Site Scripting Through Link Attachments
• Update details on blog

This release addresses XSS and user-injected auto-redirect vulnerabilities within the page content & attachment components of BookStack. These are primarily a concern if untrusted users can edit content on your BookStack instance. Please view the above report or blogpost links for more detail.