Add unread mention badging to conversation list.

app/src/main/res/drawable/ic_at_12.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="12dp"
+    android:height="12dp"
+    android:viewportWidth="12"
+    android:viewportHeight="12">
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="M11,5.44c0,1.96 -0.87,3.27 -2.31,3.27 -0.7,0 -1.3,-0.42 -1.38,-1.03h-0.05c-0.26,0.62 -0.84,0.98 -1.56,0.98 -1.28,0 -2.14,-1.05 -2.14,-2.61s0.88,-2.54 2.14,-2.54c0.66,0 1.25,0.34 1.49,0.87h0.05v-0.75h0.93v3.6c0,0.4 0.22,0.68 0.69,0.68 0.73,0 1.27,-0.9 1.27,-2.49 0,-2.23 -1.69,-3.73 -4.14,-3.73S1.88,3.51 1.88,6.08c0,2.78 1.85,4.31 4.32,4.31 0.82,0 1.66,-0.12 2.06,-0.29v0.77c-0.54,0.19 -1.28,0.3 -2.07,0.3 -3,0 -5.18,-1.82 -5.18,-5.13C1.01,2.98 3.1,0.92 6.08,0.92s4.92,1.81 4.92,4.52ZM4.55,6.07c0,1.07 0.49,1.72 1.3,1.72s1.38,-0.67 1.38,-1.72 -0.53,-1.71 -1.37,-1.71 -1.31,0.64 -1.31,1.71Z"/>
+</vector>

app/src/main/res/drawable/ic_at_20.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="20dp"
+    android:height="20dp"
+    android:viewportWidth="20"
+    android:viewportHeight="20">
+  <path
+      android:fillColor="#FF000000"
+      android:pathData="M18.33,9.07c0,3.27 -1.45,5.45 -3.85,5.45 -1.17,0 -2.17,-0.7 -2.29,-1.72h-0.08c-0.44,1.03 -1.39,1.63 -2.6,1.63 -2.13,0 -3.56,-1.75 -3.56,-4.35s1.46,-4.23 3.56,-4.23c1.1,0 2.09,0.57 2.48,1.44h0.08v-1.25h1.55v6.01c0,0.67 0.37,1.14 1.16,1.14 1.22,0 2.12,-1.49 2.12,-4.14 0,-3.71 -2.82,-6.22 -6.9,-6.22S3.12,5.86 3.12,10.13c0,4.64 3.09,7.18 7.2,7.18 1.37,0 2.76,-0.19 3.43,-0.49v1.29c-0.9,0.32 -2.13,0.5 -3.45,0.5 -4.99,0 -8.63,-3.04 -8.63,-8.54C1.67,4.97 5.15,1.54 10.13,1.54s8.21,3.02 8.21,7.53ZM7.59,10.12c0,1.78 0.82,2.87 2.16,2.87s2.3,-1.12 2.3,-2.87 -0.89,-2.85 -2.28,-2.85 -2.18,1.06 -2.18,2.85Z"/>
+</vector>