Enhancement: Add Spotless to auto format files

[davewichers]

@spassarop - I maintain OWASP Benchmark and this year we added the Maven spotless plugin to the project and it's CI to autoformat code, and verify any pull requests have also done so before submitting any code changes. While this isn't a huge deal for AntiSamy, it's relatively easy to add.

Here's the pom entry: https://github.com/OWASP-Benchmark/BenchmarkJava/blob/master/pom.xml#L1067

Any objections to doing this? We'd have to run it once to reformat ALL the code, but then after that it will only reformat files that have changed in git.

[spassarop]

No objections. Do you want to do this after pending PRs are merged or by adding it to CI it doesn't matter?

[davewichers]

I think I'll wait until 1.6.5 is ready to ship and add it to main right before the release.

[davewichers]

This was done as part of the 1.7.0 release.