chore: add readme for markdown check

docs/src/guides/markdown.md

@@ -0,0 +1,58 @@
+---
+icon: material/simple-markdown
+---
+
+# Markdown Check
+
+## Introduction
+
+Markdown file checking is integrated into the `check` pipeline.
+The reference to the pipeline can be found [here](https://input-output-hk.github.io/catalyst-ci/onboarding/).
+The goal of the `check` stage is to ensure the overall health of the project.
+Specifically, for markdown checks, it ensures that all markdown files follow valid rules.
+
+## Configuration
+
+Each repo will need two configuration files in the root of the repository:
+
+* `.markdownlint.jsonc` - Configures individual markdown rules.
+* `.markdownlint-cli2.jsonc` - Configures the CLI Tool.
+
+References to the rules can be read [here](https://github.com/DavidAnson/markdownlint/)
+
+## How it works
+
+### Locally
+
+#### Running check
+
+Executing `earthly +check` will automatically run all checks, including the verification of markdown files in the repository.
+To view the specific checks performed during the `check` stage, use the command `earthly doc`.
+
+#### Running markdown fix
+
+If an error occurs, `earthly +markdown-check-fix` can be used to automatically fix the error.
+<!-- markdownlint-disable max-one-sentence-per-line -->
+!!! Note
+    Please note that this command will fix the issues based on the capabilities of the linter.
+<!-- markdownlint-enable max-one-sentence-per-line -->
+
+### Remotely
+
+#### Running check
+
+Running `check` stage can be done by referencing to the `check` target created in this repository by adding
+
+``` Earthfile
+IMPORT github.com/input-output-hk/catalyst-ci/:<tag>
+```
+
+## Disable markdownlint rules
+
+Markdown linter rules can be disable for specific file or lines.
+
+``` html
+<!-- markdownlint-disable rules -->
+```
+
+For more example, please refer to this [doc](https://github.com/DavidAnson/markdownlint/#configuration)