Added new projects directory to host submodules to other REST project repositories

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "libraries/axion"]
 	path = libraries/axion
 	url = git@lfna.unizar.es:iaxo/RestAxionLib.git
+[submodule "projects/basic-readouts"]
+	path = projects/basic-readouts
+	url = git@lfna.unizar.es:gifna/basic-readouts.git

projects/README.md

+
+This directory will serve to link external repositories as a submodule and include different REST projects. For the moment, we will host here `basic-readouts`, `basic-geometry` and `basic-simulations` that can also be used for validation.

basic-readouts @ 59bae8e8

+Subproject commit 59bae8e88c8bd9edfdda78c567bd187db8520564