Add README file to the examples for workflows (#56)

Specify clearly that all the examples require the SSSP family
to be installed. Some further solutions for people willing to
use their own pseudopotentials, and having trouble downloading
or installing the SSSP, are also provided.

examples/workflows/README.md

@@ -0,0 +1,27 @@
+# General information
+
+All the examples make use of the `get_builder_from_protocol` to help filling all the necessary information.
+This means you need to install the compatible SSSP library via `aiida-pseudo`.
+
+For instance:
+
+```console
+aiida-pseudo install sssp -v 1.3 -x PBEsol
+```
+
+If you cannot download, and/or you want to use your own pseudo-potentials, you can still download separately the files on the [_Materials Cloud Archive_](https://archive.materialscloud.org/record/2023.65) (search for _SSSP_ if this link doesn't work). Then, you can proceed by installing a `CutoffsPseudoPotentialFamily`, i.e. a family of pseudo-potentials with pre-defined cutoffs.
+
+See [here](https://aiida-pseudo.readthedocs.io/en/latest/howto.html#adding-recommended-cutoffs) for further instructions.
+
+Then you will need to specify the `pseudo_family` you created in the `overrides`. Where to specify it depends on the `WorkChain` you are using. For example, in the case of the `IRamanSpectraWorkChain` the two places are:
+
+```
+dielectric:
+    scf:
+        pseudo_family: 'YourPseudoFamilyWithCutoff' # replace here with the label you created your family
+phonon:
+    scf:
+        pseudo_family: 'YourPseudoFamilyWithCutoff' # replace here with the label you created your family
+```
+
+In general, everywhere where the inputs of the `PwBaseWorkChain` are _exposed_. In the previous example, these inputs are exposed under the `scf` namespace.