Improve README example

Author: randyzwitch

README.md

@@ -15,8 +15,24 @@ import streamlit as st
 from streamlit_folium import folium_static
 import folium
 
-m = folium.Map(location=[45.5236, -122.6750])
-folium_static(m)
+"# streamlit-folium"
+
+with st.echo():
+    import streamlit as st
+    from streamlit_folium import folium_static
+    import folium
+
+    # center on Liberty Bell
+    m = folium.Map(location=[39.949610, -75.150282], zoom_start=16)
+
+    # add marker for Liberty Bell
+    tooltip = "Liberty Bell"
+    folium.Marker(
+        [39.949610, -75.150282], popup="Liberty Bell", tooltip=tooltip
+    ).add_to(m)
+
+    # call to render Folium map in Streamlit
+    folium_static(m)
 ```
 
 !["streamlit_folium example"](_static/streamlit_folium_example.png)

_static/streamlit_folium_example.png

@@ -0,0 +1,2 @@
+streamlit>=0.63
+streamlit-folium

examples/requirements.txt

@@ -0,0 +1,23 @@
+import streamlit as st
+from streamlit_folium import folium_static
+import folium
+
+"# streamlit-folium"
+
+with st.echo():
+    import streamlit as st
+    from streamlit_folium import folium_static
+    import folium
+
+    # center on Liberty Bell
+    m = folium.Map(location=[39.949610, -75.150282], zoom_start=16)
+
+    # add marker for Liberty Bell
+    tooltip = "Liberty Bell"
+    folium.Marker(
+        [39.949610, -75.150282], popup="Liberty Bell", tooltip=tooltip
+    ).add_to(m)
+
+    # call to render Folium map in Streamlit
+    folium_static(m)
+