Move app.py to top level

To see if spaces finds the file then, it does not
find it in the hexviz directory, with the current
README.md config.

app.py

@@ -0,0 +1,44 @@
+import py3Dmol
+import stmol
+import streamlit as st
+from stmol import showmol
+
+from hexviz.attention import Model, ModelType, get_attention_pairs
+
+st.sidebar.title("pLM Attention Visualization")
+
+st.title("pLM Attention Visualization")
+
+# Define list of model types
+models = [
+    Model(name=ModelType.TAPE_BERT, layers=12, heads=12),
+]
+
+selected_model_name = st.selectbox("Select a model", [model.name.value for model in models], index=0)
+selected_model = next((model for model in models if model.name.value == selected_model_name), None)
+
+pdb_id = st.text_input("PDB ID", "4RW0")
+
+left, right = st.columns(2)
+with left:
+    layer_one = st.number_input("Layer", value=1, min_value=1, max_value=selected_model.layers)
+    layer = layer_one - 1
+with right:
+    head_one = st.number_input("Head", value=1, min_value=1, max_value=selected_model.heads)
+    head = head_one - 1
+
+min_attn = st.slider("Minimum attention", min_value=0.0, max_value=0.4, value=0.1)
+
+attention_pairs = get_attention_pairs(pdb_id, layer, head, min_attn, model_type=selected_model.name)
+
+def get_3dview(pdb):
+    xyzview = py3Dmol.view(query=f"pdb:{pdb}")
+    xyzview.setStyle({"cartoon": {"color": "spectrum"}})
+    stmol.add_hover(xyzview, backgroundColor="black", fontColor="white")
+    for att_weight, first, second in attention_pairs:
+        stmol.add_cylinder(xyzview, start=first, end=second, cylradius=att_weight*3, cylColor='red', dashed=False)
+    return xyzview
+
+
+xyzview = get_3dview(pdb_id)
+showmol(xyzview, height=500, width=800)