Add titlebar in about page

This addition will provide easy navigation back to the main menu,
as well as improve the user experience and consistent design.

app/src/main/java/com/github/tmo1/sms_ie/AboutActivity.kt

@@ -30,5 +30,13 @@ class AboutActivity : AppCompatActivity() {
         setContentView(R.layout.activity_about)
         val aboutText: TextView = findViewById(R.id.aboutText)
         aboutText.text = getString(R.string.app_about_text, BuildConfig.VERSION_NAME)
+        setSupportActionBar(findViewById(R.id.toolbar))
+        supportActionBar?.setTitle(R.string.about)
+        supportActionBar?.setDisplayHomeAsUpEnabled(true)
     }
-}
+
+    override fun onSupportNavigateUp(): Boolean {
+        finish()
+        return true
+    }
+}

app/src/main/res/layout/activity_about.xml

@@ -18,17 +18,24 @@
   ~ along with SMS Import / Export.  If not, see <https://www.gnu.org/licenses/>.
   -->
 
-<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"
-    tools:context=".AboutActivity">
+    android:layout_height="wrap_content"
+    android:orientation="vertical">
 
-    <androidx.constraintlayout.widget.ConstraintLayout
+    <include layout="@layout/app_bar" />
+
+    <ScrollView
         android:layout_width="match_parent"
         android:layout_height="wrap_content">
 
+    <androidx.constraintlayout.widget.ConstraintLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        tools:context=".AboutActivity">
+
     <TextView
         android:id="@+id/aboutText"
         android:layout_width="wrap_content"
@@ -158,4 +165,6 @@
 
     </androidx.constraintlayout.widget.ConstraintLayout>
 
-</ScrollView>
+    </ScrollView>
+
+</LinearLayout>

app/src/main/res/layout/app_bar.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.appcompat.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:id="@+id/toolbar"
+    android:layout_width="match_parent"
+    android:layout_height="?attr/actionBarSize"
+    android:background="?attr/colorPrimary"
+    android:minHeight="?attr/actionBarSize"
+    android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
+    app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
+    app:titleTextAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Title"
+    app:subtitleTextAppearance="@style/TextAppearance.Widget.AppCompat.Toolbar.Subtitle" />