Add SAST security checks with SECURITY.md #178

This commit incorporates Static Analysis Security Testing (SAST) using
CodeQL. This integration will enforce consistent security assessments
with every change and on a predetermined schedule.

This commit also involves a restructure of security checks. The existing
security-checks workflow is renamed to better reflect its functionality
related to dependency audits.

These changes will enhance the project's resilience against potential
vulnerabilities in both the codebase and third-party dependencies.

Changes include:

- Remove older LGTM badge that's replaced by SAST checks.
- Rename `checks.security.yaml` to `checks.security.dependencies.yaml`,
  reinforcing the focus on dependency audits.
- Update `README.md`, ensuring the clear representation of security
  check statuses, including new SAST integration.
- Add new `SECURITY.md`, establishing the protocol for reporting
  vulnerabilities and outlining the project's commitment to robust
  security testing.
- Enhance `docs/tests.md` with detailed information on the newly
  integrated security checks.
- Add reference to SECURITY.md in README.md.

docs/tests.md

@@ -56,6 +56,11 @@ These checks validate various qualities like runtime execution, building process
 - Use [various tools](./../package.json) and [scripts](./../scripts).
 - Are automatically executed as [GitHub workflows](./../.github/workflows).
 
+### Security checks
+
+- [`checks.security.sast`](./../.github/workflows/checks.security.sast.yaml): Utilizes CodeQL to conduct Static Analysis Security Testing (SAST) to ensure the secure integrity of the codebase.
+- [`checks.security.dependencies`](./../.github/workflows/checks.security.dependencies.yaml): Performs audits on third-party dependencies to identify and mitigate potential vulnerabilities, safeguarding the project from exploitable weaknesses.
+
 ## Tests structure
 
 - [`package.json`](./../package.json): Defines test commands and includes tools used in tests.