Create README.md to scripts directory

scripts/README.md

+# Public APIs Scripts
+
+This directory contains all validation and testing scripts used by Public APIs.
+
+```bash
+scripts
+│   github_pull_request.sh  # used to validate changes of a pull request
+│   requirements.txt  # contains dependencies of validate package
+│
+├───tests  # contains all unit tests from the validate package
+│       test_validate_format.py
+│       test_validate_links.py
+│
+└───validate  # validate package
+        format.py
+        links.py
+```
+
+## Running Tests
+
+To run all tests it is necessary to change to the scripts directory:
+
+```bash
+$ cd scripts
+```
+
+then run:
+
+```bash
+$ python -m unittest discover tests/ --verbose
+```
+
+To run only the format tests, run:
+
+```bash
+$ python -m unittest discover tests/ --verbose --pattern "test_validate_format.py"
+```
+
+To run only the links tests, run:
+
+```bash
+$ python -m unittest discover tests/ --verbose --pattern "test_validate_links.py"
+```
+
+*Note that it is necessary to have [python](https://www.python.org/) installed.*