Check length of descriptions for F-Droid (#1083)

* Check length of descriptions for F-Droid

Fixes #1080

* Shorten en-US string

config/travis/validate_fastlane_metadata.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+exitcode=0
+
+for file in fastlane/metadata/android/*/full_description.txt
+do
+    chars=$(cat $file | wc -m)
+    if [ "$chars" -gt 4000 ]
+    then
+        echo "$file too long"
+        let exitcode++
+    fi
+done
+
+for file in fastlane/metadata/android/*/short_description.txt
+do
+    chars=$(cat $file | wc -m)
+    if [ "$chars" -gt 80 ]
+    then
+        echo "$file too long"
+        let exitcode++
+    fi
+done
+
+exit $exitcode