fix(docs): Update instructions for building documentation

Author: andresailer

docs/README

@@ -3,17 +3,24 @@ How to build DIRAC documentation
 
 1. Create DIRAC client environment by an appropriate
    source bashrc
+   or
+   source diracos/diracosrc
+
+1.1 Depending on how you installed DIRAC you might need to install
+   pip install sphinx_rtd_theme sphinx_design
 
 2. Go to the Documentation directory of the DIRAC source code repository
    cd DIRAC/docs/
-   export PYTHONPATH=$PWD/diracdoctools:$PYTHONPATH
+   export PYTHONPATH=$PWD:$PYTHONPATH
 
 3. Run the documentation building script
 
    This also creates all the automatically generated rst files
 
       make htmlall
 
+   Note: You must avoid having the string "test" in your folder structure or no code documentation will be created.
+
 3.1 to run incremental builds after rst files have changed, only run
 
    make html