Allow passing document and release-notes flags

[RomainCscn]

Similar to #92, this time both for documents and release notes.

• documents can be chained, same as links, either via an inline flag --document or --document-file
• release notes can only be passed once (passing multiple times will just be last-one-win), and can also be set as --release-notes or release-notes-file

Follows convention that can be find used in gh, kubectl or terraform.

---

⚠️ Should only be merged after the API PR: https://github.com/linear/linear-app/pull/75514

[linear-code]

LIN-71393

[axelniklasson]

Do we need two flags per entity type? Seems like we could infer whether we point it towards a file or pass in raw content. Not a big deal but feels a little noisy to have all these arguments we can pass in.

[RomainCscn]

I preferred to align with how the most major CLI do it.

--notes <string>
    Release notes
--notes-file <file>
    Read release notes from file (use "-" to read from standard input)

for example for gh

(preferred to keep the full name release-notes)