Make text in logs view selectable

disable updating when text is selected

Closes #105

app/src/main/java/com/github/gotify/log/LogsActivity.java

@@ -74,7 +74,9 @@ public class LogsActivity extends AppCompatActivity {
         @Override
         protected void onPostExecute(String s) {
             TextView content = findViewById(R.id.log_content);
+            if (content.getSelectionStart() == content.getSelectionEnd()) {
                 content.setText(s);
+            }
             super.onPostExecute(s);
         }
     }

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

@@ -26,6 +26,7 @@
                 android:layout_marginEnd="8dp"
                 android:layout_marginBottom="8dp"
                 android:text=""
+                android:textIsSelectable="true"
                 android:textSize="10sp"
                 app:layout_behavior="@string/appbar_scrolling_view_behavior"
                 app:layout_constraintBottom_toBottomOf="parent"