doc: add missing instructions to generate and check the documentation

- When a new Test Case is created, it has to be declared in the corresponding `doc/tests/test_{group}.py` Python file

  (where `{group}` represents the group of operations and how they are defined in the ETSI RGS/CIM-0012v211 document). 

  It includes the creation of the corresponding expected result inside the `doc/files` folders to compare the generation 

  of the documentation. Complementary to this, updates have to be done:

  Complementary to this, updates have to be done:

  - In `doc/analysis/initial_setup.py` if it uses a new keyword to set up the initial state of the Test Case

  - In `doc/analysis/requests.py` if it updates an endpoint operation, for instance by adding support for a new request

    parameter (in `self.op` with the list and position of parameters, in the method that pretty prints the operation in 

    the automated generation of the documentation associated with the Test Cases. If the positions array is empty, it 

    means that all the parameters will be taken into consideration)

  - Run the documentation generation script (`python doc/generateDocumentationData.py {new_tc_id}`) for the new Test 

    Case and copy the generated JSON file in the folder containing all files for the given group and subgroup 

    (`cp doc/results/{new_tc_id}.json doc/files/{group}/{sub-group}`)

- When a new global Keyword is created, it has to be declared in the corresponding Python files:

  - In `doc/analysis/checks.py` if it is an assertion type keyword (in `self.checks` to reference the method that pretty

    prints the operation and `self.args` to identify the position of the arguments) and the corresponding method to 

- When a new directory containing Test Cases is created, it has to be declared in `doc/generaterobotdata.py` along with

  its acronym

Then a new version of the documentation can be generated by running the `doc/generateDocumentationData.py` Python script.

Finally, check that everything is OK by running the unit tests:

```shell

python -m unittest discover -s ./doc/tests -t ./doc

```

### Run configurations (PyCharm)