Added JCharset

ATTRIBUTION.md

@@ -20,3 +20,4 @@ FairEmail uses:
 * [Color Picker](https://github.com/QuadFlask/colorpicker). Copyright 2014-2017 QuadFlask. [Apache License 2.0](https://github.com/QuadFlask/colorpicker#user-content-license).
 * [Bouncy Castle](https://www.bouncycastle.org/). Copyright (c) 2000 - 2019 The Legion of the Bouncy Castle Inc. [MIT License](https://www.bouncycastle.org/licence.html).
 * [AppAuth for Android](https://github.com/openid/AppAuth-Android). Copyright 2015 The AppAuth for Android Authors. All Rights Reserved. [Apache License 2.0](https://github.com/openid/AppAuth-Android/blob/master/LICENSE).
+* [JCharset](http://www.freeutils.net/source/jcharset/). Copyright (C) 1989, 1991 Free Software Foundation, Inc. [GNU General Public License](http://www.freeutils.net/source/jcharset/#license).

app/build.gradle

@@ -257,6 +257,7 @@ dependencies {
     def bouncycastle_version = "1.64"
     def colorpicker_version = "0.0.15"
     def appauth_version = "0.7.1"
+    def jcharset_version = "2.1"
 
     // https://developer.android.com/jetpack/androidx/releases/
 
@@ -388,4 +389,7 @@ dependencies {
     // https://github.com/openid/AppAuth-Android
     // https://mvnrepository.com/artifact/net.openid/appauth?repo=bt-openid
     implementation "net.openid:appauth:$appauth_version"
+
+    // http://www.freeutils.net/source/jcharset/
+    implementation "net.freeutils:jcharset:$jcharset_version"
 }

app/src/main/assets/ATTRIBUTION.md

@@ -20,3 +20,4 @@ FairEmail uses:
 * [Color Picker](https://github.com/QuadFlask/colorpicker). Copyright 2014-2017 QuadFlask. [Apache License 2.0](https://github.com/QuadFlask/colorpicker#user-content-license).
 * [Bouncy Castle](https://www.bouncycastle.org/). Copyright (c) 2000 - 2019 The Legion of the Bouncy Castle Inc. [MIT License](https://www.bouncycastle.org/licence.html).
 * [AppAuth for Android](https://github.com/openid/AppAuth-Android). Copyright 2015 The AppAuth for Android Authors. All Rights Reserved. [Apache License 2.0](https://github.com/openid/AppAuth-Android/blob/master/LICENSE).
+* [JCharset - Java Charset package](http://www.freeutils.net/source/jcharset/). Copyright (C) 1989, 1991 Free Software Foundation, Inc. [GNU General Public License](http://www.freeutils.net/source/jcharset/#license).