#108 docs(readme): add send examples for every message type

[Anonymous]

Originally created by: ded-furby

Summary

• add copy-paste curl examples for every supported send message endpoint in the README API section
• keep the payloads aligned with the current controller DTOs for media, interactive, reaction, location, and contact sends
• leave the existing text-message example in place and expand the section around it for the remaining message types

Related issues

Closes [#104]

Test plan

• [x] Checked each example against the current request DTOs in packages/wa-server/src/messages/dto/*
• [x] Ran git diff --check
• [ ] Tested in browser (docs-only change)