Stop on "Streamer(*)" model selection and minor text changes

- Now the execution stops on Streamer model selection
- Changes in README.md

HDPt_app.py

@@ -135,6 +135,9 @@ def run():
     with st.sidebar.expander('Magnetic fieldlines configuration:', expanded=False):
         fls_model_ = st.radio('', ['Radial','Parker spiral(*)','Streamer(*)'])
         st.markdown('(*) Mode not implemented yet')
+        if fls_model_ == 'Streamer(*)':
+            st.warning('This mode is not implemented yet.')
+            st.stop()
     with st.sidebar.expander('Density models:', expanded=False):
         density_model_ = st.radio('', ['Saito','Newkirk','Leblanc'])
         nfold_value = st.number_input('N-fold number', 0.5, 5., 1., step=0.1)

README.md

@@ -65,6 +65,10 @@ The application should now open in the default browser!
 
 Complete documentation of the _HDPmt_ can be found in HDPmt_doc.ipynb.
 
+## Acknowledging or Citing HDPmt
+
+If you use HDPmt for work or research presented in a publication, please cite this package by including in the Acknowledgement section the following: "This research has made use of HDPmt v?.?.? (fill the version), an open-source and free Python package (include zenodo citation here) developed to model the propagation of a heliospheric disturbance.". Include the HDPmt citation in your paper's reference list.
+
 ## 📦 Usefull python packages:
         
 - [SunPy](https://sunpy.org/): The community-developed, free and open-source solar data analysis environment for Python.