FAQ: Add "I don't like copyright headers" section

[n0toose]

• https://reuse.software/faq/ mentions the addition of REUSE.toml.
• Efforts to adapt REUSE can be (somewhat rightfully) rejected because of the whole copyright header thing, which is a matter of preference sometimes (and, after all, if someone needs to "copy things from another project", one may imagine that they can prepend a header themselves).
• Answering that question (while emphasizing that, perhaps, it's best to use the SPDX headers and emphasize how it's a standard - and how projects like the Rust compiler do embed their licenses in a LICENSES directory) could help increase overall adoption, albeit not perfectly?

[n0toose]

I would not mind actually working on this issue myself, but it'd be great if a maintainer could answer whether the approach that I'd be taking (as loosely described in the Issue) seems like the right way to go first - writing free text is a lot of effort and I'd like to spare some review rounds. :D