v0.2.0

Added

• The version shows in the toolbar.
• After an update the app shows what changed, once, as a popup. Dismiss it and
  it stays dismissed.
• --version prints the build and exits before a window opens, so scripts and
  packaging can ask which version is installed.
• An install script, packaging/install.sh, that puts the app in
  ~/.local/bin and adds it to the desktop launcher.
• An application icon.

Fixed

• Windows no longer opens a console window behind the app.
• Camera streams that are not the shape of their tile are letterboxed rather
  than cropped.
• The label bar on a tile no longer covers the bottom of the picture.

Changed

• Every release now carries written notes. The release workflow publishes the
  matching section of CHANGELOG.md, and a tag without one fails the build.