General
- Reworked "Open Viewer" (see #246)
- Exported messages are loaded from the app, similarly to downloaded files
- Significantly reduced time to load the viewer and memory usage
- It is now possible to view much larger archives in browsers that were previously unable to load them
- "Save Viewer" has been removed, as it's incompatible with the new viewer and downloaded files
- Fixed broken links to image embeds (since v41.0)