add known to work summary

KnownToWork/Summary.md

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+# Known to work
+## App Stores
+
+1. [F-Droid](F-Droid.md), the OpenSource app store
+2. [Aurora Store](AuroraStore.md), googels paly store accessed anonymously
+
+## Browser
+
+1. [Fennec](Fennec.md), firefox for mobile
+
+## Messaging
+
+1. [Signal](Signal.md), messaging over signals server, encrypted
+2. [DeltaChat](DeltaChat.md), messaging over email, auto-encrypted
+3. [Telegram](Telegram.md), messaging over somehows server, not encrypted, reads your contacts, not recomended
+
+## Calendar, Contacts & Files
+
+1. Finde some ideas described here: [Sync your data](sync_calendar.md)
+
+## Navigation
+
+1. [OsmAnd](OsmAnd.md), uses Open-Streetmap maps for offline navigation (pdestrian, cycle, car, truck ...), speech output possible.