update polity map playRate to be same as world map

seshat/apps/core/templates/core/polity_map.html

@@ -28,8 +28,17 @@
                         <label for="playButton">Run animation:</label>
                         <button id="playButton" type="button" onclick="startPlay()">▶️</button>
                         <button id="stopButton" type="button" onclick="stopPlay()">⏸</button><br>
-                        <label for="playRate">Animation speed:</label>
-                        <input type="range" name="playRate" id="playRate" min="1" max="5" value="2" class="slider" onchange="plotPolities()"><br>
+                        <label for="playRate">Speed: </label>
+                        <input type="range" name="playRate" id="playRate" min="1" max="5" value="2" class="slider" list="tickmarks"
+                            onchange="updateSliderValue(this.value)">
+                        <datalist id="tickmarks">
+                            <option value="1"></option>
+                            <option value="2"></option>
+                            <option value="3"></option>
+                            <option value="4"></option>
+                            <option value="5"></option>
+                        </datalist>
+                        <span id="sliderValue">5 y/s</span><br>
                         <label for="opacitySlide">Opacity:</label>
                         <input type="range" name="opacitySlide" id="opacitySlide" min="0.1" max="1" step="0.1" value="0.5" class="slider" onchange="plotPolities()" style="width: 150px;">
                     </div>