ci: Update Superlinter to only include src/ (#65)

Author: holtskinner

.github/linters/.markdownlint.json

@@ -62,6 +62,5 @@ jobs:
           VALIDATE_JAVASCRIPT_STANDARD: false
           VALIDATE_TYPESCRIPT_STANDARD: false
           VALIDATE_GIT_COMMITLINT: false
-          MARKDOWN_CONFIG_FILE: .markdownlint.json
           PYTHON_MYPY_CONFIG_FILE: .mypy.ini
-          FILTER_REGEX_EXCLUDE: "^examples/.*$|^CHANGELOG\\.md$"
+          FILTER_REGEX_INCLUDE: "^src/**"