feat: add FesodDoc classes with initial structure

[psxjoy]

Purpose of the pull request

What's changed?

Checklist

• I have read the Contributor Guide.
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.

[bengbengbalabalabeng]

We could try to move the <licenseHeader> configuration of spotless-maven-plugin down to the current module, so it only applies to the fesod-doc files, avoiding any impact on historical files in other existing modules while also eliminating the need to manually maintain license headers.