SALOME 7.3.0 preparation : add Release Notes file

diff --git a/SALOME_7_3_0_Release_Notes.pdf b/SALOME_7_3_0_Release_Notes.pdf
new file mode 100755 (executable)
index 0000000..99f36ef
Binary files /dev/null and b/SALOME_7_3_0_Release_Notes.pdf differ