Include the checksum hash for Atlassian Companion binaries on the download pages to verify file integrity.

This is a common industry security practice already adopted for other products, such as Confluence and Crowd.

Identified pages with download links where the checksum hash can be included:

• https://confluence.atlassian.com/doc/atlassian-companion-app-release-notes-958455712.html
• https://confluence.atlassian.com/doc/install-atlassian-companion-992678880.html
• https://confluence.atlassian.com/doc/administering-the-atlassian-companion-app-958456281.html