extras: add Thunderbird Conversations extension

- https://addons.thunderbird.net/thunderbird/addon/gmail-conversation-view/
- fixes #18

CHANGELOG.md

@@ -9,6 +9,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 - packages: system/virtualization: add [libguestfs-tools](https://packages.debian.org/libguestfs-tools), [virt-p2v](https://packages.debian.org/virt-p2v), [libguestfs-rsync](https://packages.debian.org/libguestfs-rsync), [libguestfs-rescue](https://packages.debian.org/libguestfs-rescue)
 - packages: internet: add [purple-discord](https://packages.debian.org/bullseye/purple-discord) (Discord messaging service plugin for pidgin/libpurple)
 - packages: development: add [mgitstatus](https://github.com/fboender/multi-git-status) (show status of multiple Git repositories)
+- extras: add [Thunderbird Conversations](https://addons.thunderbird.net/thunderbird/addon/gmail-conversation-view/) extension
+
 
 ### Removed
 - packages: remove [gnome-clocks](https://packages.debian.org/bullseye/gnome-clocks)

Makefile.extra

@@ -40,3 +40,7 @@ download_extra: clean
 	mkdir -p config/includes.chroot/usr/lib/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}
 	$(WGET) https://addons.mozilla.org/firefox/downloads/file/3465157/keepassxc_browser-latest-fx.xpi -O config/includes.chroot/usr/lib/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}/keepassxc-browser@keepassxc.org.xpi
 	$(WGET) https://addons.mozilla.org/firefox/downloads/file/3711829/cookie_autodelete-3.6.0-an+fx.xpi -O config/includes.chroot/usr/lib/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}/CookieAutoDelete@kennydo.com.xpi
+
+	# EXTRA https://addons.thunderbird.net/thunderbird/addon/gmail-conversation-view/
+	mkdir -p config/includes.chroot/usr/lib/thunderbird/extensions/
+	$(WGET) https://addons.thunderbird.net/thunderbird/downloads/latest/gmail-conversation-view/addon-54035-latest.xpi -O config/includes.chroot/usr/lib/thunderbird/extensions/gconversation@xulforum.org.xpi