chore: Add x/capability docs

[facundomedica]

Description

Add and fix documentation for x/capability module

Closes: #11793

---

Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[codecov]

Codecov Report

Merging #11922 (02032aa) into main (90272e3) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main   #11922      +/-   ##
==========================================
- Coverage   66.02%   66.00%   -0.02%     
==========================================
  Files         676      675       -1     
  Lines       71346    71282      -64     
==========================================
- Hits        47105    47053      -52     
+ Misses      21559    21551       -8     
+ Partials     2682     2678       -4     

Impacted Files	Coverage Δ
x/capability/types/keys.go	100.00% <ø> (ø)
crypto/keys/internal/ecdsa/privkey.go	82.45% <0.00%> (-1.76%)	⬇️
core/appconfig/config.go

[alexanderbez]

I would love to see the entire spec and doc under a single README. WDYT? We've done this for some modules afaik.

[facundomedica]

I don't see any other module doing everything in a single file, at least in the ones in this repo 🤔

[alexanderbez]

Ahh, ok. Well I propose that haha. WDYT?

[facundomedica]

mmm yeah, for this module it would make sense given that it's a very short documentation (but would break consistency). For other modules, I don't think that would work, remember that we are rendering these files here: https://docs.cosmos.network/main/modules/capability/

Another option would be to have a script that collects all of the md files in a module's spec and puts them into a single file and we publish those somewhere else (titled: docs for real devs that will read this in a code editor and not in their browsers lol).