spotless and markdown

[slawekjaranowski]

We need check only project markdown files.
Generated files from target should be excluded.

Reproduce, eg in tidy-maven-plugin execute site build twice:

mvn site

mvn site 

we have:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-site-plugin:3.12.1:site (default-site) on project tidy-maven-plugin: failed to get report for org.apache.maven.plugins:maven-plugin-report-plugin: Failed to execute goal com.diffplug.spotless:spotless-maven-plugin:2.43.0:check (spotless-check) on project tidy-maven-plugin: The following files had format violations:
[ERROR]     target/site/apidocs/legal/jquery.md
[ERROR]         @@ -1,6 +1,7 @@
[ERROR]          ##·jQuery·v3.6.1
[ERROR]          
[ERROR]          ###·jQuery·License
[ERROR]         +
[ERROR]          ```
....

[slawekjaranowski]

@slachiewicz can you look 😄

[slachiewicz]

https://github.com/mojohaus/mojo-parent/blob/31f1276f1d5a750be596befcaa379a356ec278f9/pom.xml#L599C13-L604C24

include:
.md
src/site/markdown/**/.md

[slawekjaranowski]

maybe:

                <include>*.md</include>
                <include>src/**/.md</include>