Update `rebar3_sbom` HexDocs to the new documentation format & expand the doc

[IciaCarroBarallobre]

Summary

Update rebar3_sbom HexDocs to the new documentation format and expand with more comprehensive documentation, examples, and use cases.

Current Issues

• Documentation uses old pre-hexdocs format
• Limited examples
• Difficult to follow

References

• Rebar3 sbom plugin, current docs
• Erlang Documentation System - Official guidelines, which is also an example of the new format of rebar3 ex_doc :)