nip34 issues: compatibility with gitworkshop.dev and other clients

its not explicit in nip34 but gitworkshop.dev uses the first line of the content as the title of an issue. voyage is using the `subject` tag for titles.

It was probably a coin flip about which approach is better. using the first line of content, means it's less effort for other client to implement, and at a minimum they can just display the `content` and it will look fine.

many clients now display nip34 issues and expect the above format. This means in amethyst, Nostter, nostrudel, coracle, gitworkshop, etc your issues are getting displayed without their title.

Would you consider switching approaches? The nip should probably be explicit about this.