Documentation on how to sign Cosmos transactions

[zmanian]

Update documentation to include details on how to sign Cosmos transactions for service providers.

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #3968 into develop will increase coverage by 1.03%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #3968      +/-   ##
===========================================
+ Coverage    60.45%   61.48%   +1.03%     
===========================================
  Files          196      186      -10     
  Lines        14485    13978     -507     
===========================================
- Hits          8757     8595     -162     
+ Misses        5147     4836     -311     
+ Partials       581      547      -34

[cwgoes]

Notes, suggestions, a few typos.

[cwgoes]

ACK

Depending on what prompted this documentation, other things that could be worth mentioning are:

• How to compose multi-Msg transactions (likely more efficient in many cases)
• Memo limitations