add automated screenshots, fastlane metadata, and appstream metainfo

Fixes #174, fixes #173, fixes #172

integration_test/screenshots/avatars/SOURCES.md

@@ -0,0 +1,22 @@
+# Screenshot avatars
+
+Avatars for the people, rooms and spaces in the screenshots, cropped from photos on Wikimedia Commons and Public Domain Pictures that are in the public domain or CC0, so they need no attribution.
+
+| File                   | License       | Source                                                                                                   |
+| ---------------------- | ------------- | -------------------------------------------------------------------------------------------------------- |
+| pumpkin.webp           | Public domain | https://commons.wikimedia.org/wiki/File:Cucurbita_2011_G1.jpg                                            |
+| orange.webp            | Public domain | https://commons.wikimedia.org/wiki/File:Orange-fruit-2.jpg                                               |
+| log-1.webp             | CC0           | https://commons.wikimedia.org/wiki/File:Tabby_cat_with_blue_eyes-3336579.jpg (tinted green)              |
+| strudel.webp           | CC0           | https://commons.wikimedia.org/wiki/File:Strudel-de-maca-2.png                                            |
+| opal.webp              | Public domain | https://commons.wikimedia.org/wiki/File:Opal_6.jpg                                                       |
+| cinnamon.webp          | CC0           | https://commons.wikimedia.org/wiki/File:Cassia_bark_(2).jpg                                              |
+| green-tea.webp         | CC0           | https://www.publicdomainpictures.net/en/view-image.php?image=165622&picture=hot-green-tea-with-heart-art |
+| development.webp       | CC0           | https://commons.wikimedia.org/wiki/File:Code_on_computer_monitor_(Unsplash).jpg                          |
+| fediverse.webp         | Public domain | https://commons.wikimedia.org/wiki/File:Blackeyegalaxy.jpg                                               |
+| flutter-devs.webp      | CC0           | https://commons.wikimedia.org/wiki/File:Anna%27s_Hummingbird_Feeding.jpg                                 |
+| linux-mobile.webp      | CC0           | https://commons.wikimedia.org/wiki/File:Gentoo_penguin_with_a_feather_in_its_beak.jpg                    |
+| matrix-community.webp  | Public domain | https://commons.wikimedia.org/wiki/File:Earth_at_Night,_Asia_(8270740728).jpg                            |
+| off-topic.webp         | CC0           | https://commons.wikimedia.org/wiki/File:Coffee_cup_surrounded_by_coffee_beans.jpg                        |
+| open-source-games.webp | Public domain | https://commons.wikimedia.org/wiki/File:LodgeNet-Nintendo-N64-Controller.jpg                             |
+| rust.webp              | CC0           | https://commons.wikimedia.org/wiki/File:Carcinus_maenas_146434844.jpg                                    |
+| self-hosting.webp      | CC0           | https://commons.wikimedia.org/wiki/File:Legrand_S.A._server_rack.jpg                                     |