Prepare release Riot.imX v0.91.3 for the beta channel

CHANGES.md

@@ -1,6 +1,12 @@
-Changes in RiotX 0.23.0 (2020-XX-XX)
+Changes in Riot.imX 0.91.3 (2020-07-01)
 ===================================================
 
+Notes:
+ - This version is the third beta version of RiotX codebase published as Riot-Android on the PlayStore.
+ - Changelog below includes changes of v0.91.0, v0.91.1, and v0.91.2, because the first beta versions have been tagged and
+ published from the branch feature/migration_from_legacy.
+ - This version uses temporary name `Riot.imX`, to distinguish the app with RiotX app.
+
 Features ✨:
  - Call with WebRTC support (##611)
  - Add capability to change the display name (#1529)
@@ -25,12 +31,6 @@ Bugfix 🐛:
  - Searching by displayname is case sensitive (#1468)
  - Fix layout overlap issue (#1407)
 
-Translations 🗣:
- -
-
-SDK API changes ⚠️:
- - 
-
 Build 🧱:
  - Enable code optimization (Proguard)
  - SDK is now API level 21 minimum, and so RiotX (#405)

vector/build.gradle

@@ -17,7 +17,7 @@ androidExtensions {
 // Note: 2 digits max for each value
 ext.versionMajor = 0
 ext.versionMinor = 91
-ext.versionPatch = 2
+ext.versionPatch = 3
 
 static def getGitTimestamp() {
     def cmd = 'git show -s --format=%ct'