Add Javadoc build workflow

[bact]

Will publish to https://spdx.github.io/tools-java/

[goneall]

LGTM - Thanks @bact

[bact]

Needs to enable this in GitHub Settings -> Pages

[goneall]

Needs to enable this in GitHub Settings -> Pages

I enabled the pages, but it is still not showing up.

There is nothing in the gh-pages branch and the action log showed success for the gh-pages deployment, but the artifact size is very small - so it looks like the JavaDocs has not been generated:

[build](https://github.com/spdx/tools-java/actions/runs/18288867655/job/52070890512#logs)
succeeded 14 minutes ago in 4s
Search logs
1s
1s
0s
Run actions/upload-pages-artifact@v3
Run echo ::group::Archive artifact
Archive artifact
Run actions/upload-artifact@v4
With the provided path, there will be 1 file uploaded
Artifact name is valid!
Root directory input is valid!
Beginning upload of artifact content to blob storage
Uploaded bytes 266
Finished uploading artifact content to blob storage!
SHA256 digest of uploaded artifact zip is a25e1639ac13f79cbb1a50dc43a75f3787cfcd12ac1974ca47081c8780ef2359
Finalizing artifact upload
Artifact github-pages.zip successfully finalized. Artifact ID 4195125912
Artifact github-pages has been successfully uploaded! Final size is 266 bytes. Artifact ID is 4195125912
Artifact download URL: https://github.com/spdx/tools-java/actions/runs/18288867655/artifacts/4195125912

[bact]

Thank you. Will take a look more at this.

[bact]

I saw you fixed it. Thank you.