Update README.md

Author: zonca

README.md

@@ -12,3 +12,88 @@ Test that it can visualize a map:
         python test_healpyvis.py
 
 Check it creates `map.png` file.
+
+# Building PyHealpy with JupyterLite's Pyodide
+
+by @VeerioSDSC
+
+Steps include building the wheel to serve, setting up JupyterLite, and commands for the Lite cells. 
+
+### Building the PyHealpy Wheel to Serve
+
+First need to set up the pyodide compiler with the following
+
+```
+pip install pyodide-build
+git clone https://github.com/emscripten-core/emsdk.git
+cd emsdk
+PYODIDE_EMSCRIPTEN_VERSION=$(pyodide config get emscripten_version)
+./emsdk install ${PYODIDE_EMSCRIPTEN_VERSION}
+./emsdk activate ${PYODIDE_EMSCRIPTEN_VERSION}
+source emsdk_env.sh
+cd ..
+```
+
+Then building the wheel:
+
+```
+git clone https://github.com/healpy/pyhealpy.git
+cd pyhealpy
+pyodide build
+```
+It builds the wheel in a dist folder
+
+Serving the wheel locally:
+
+`python3 -m http.server --directory dist`
+
+### Using it with JupyterLite
+
+If one just wants to use another environment they can use the demo one found here: https://jupyterlite.github.io/demo/lab/index.html
+
+If one wants to deploy Lite with GitHub Pages:
+
+Template to use: https://github.com/jupyterlite/demo
+Since the initial commit will fail, go to settings→actions→general and allow read/write perms for workflows, and go to settings→pages and make sure GitHub Actions is selected as the source for Deployment. Make a commmit and then it will deploy. 
+
+If one wants to deploy Lite locally:
+
+```
+python -m pip install jupyterlite-core
+jupyter lite init
+python3 -m pip install jupyterlite-pyodide-kernel
+cd _output
+jupyter lite build
+jupyter lite serve
+```
+### Commands to Run in JupyterLite - web address for installation is based on where the wheel is served. 
+
+If locally, you might face [CORS Issue. ](https://chromewebstore.google.com/detail/moesif-origincors-changer/digfbfaphojjndkpccljibejjbppifbc?hl=en-US)
+
+Commands for the cells:
+
+```
+import micropip
+await micropip.install ("http://localhost:8000/healpy-0.1.dev1885+g71d9336-py3-none-any.whl") 
+await micropip.install("matplotlib")
+import healpy
+```
+
+Then it can be tested with the [contents of file from above](https://github.com/healpy/pyhealpy/blob/pyhealpy/test_healpyvis.py):
+
+```
+
+import healpy as hp
+import matplotlib.pyplot as plt
+
+m = hp.read_map(
+    "wmap_band_iqumap_r9_7yr_W_v4_udgraded32_masked_smoothed10deg_fortran.fits"
+);
+#link will change based on where file is 
+
+hp.projview(m, coord=["G"], projection_type="mollweide");
+
+plt.savefig("map.png")
+```
+
+