docs: improve IBC guide

[fedekunze]

Description

closes: #6484

• minor docs fixes

IBC:

• Create IBC section
• IBC overview
• IBC Integration to app.go with ICS 20 transfers only
• Create your own IBC custom app module (i.e current content)

(Follow up PR) - Ocaps:

• Complete ocap.md with capability module contents
• capability module spec update

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[colin-axner]

Ack pending updates to acknowledgement literature