feat(gnoclient): add support for MsgAddPackage

[leohhhn]

Description

This PR adds gnoclient support for MsgAddPackage, and updates the docs to match the functionality. Docs preview: https://www.loom.com/share/0dfa38e6e95e4e1195d686c8cbffa453?sid=4af29ee0-d065-442c-977e-ce9577796688

Closes #1840

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

Attention: Patch coverage is 82.85714% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 47.76%. Comparing base (831bb6f) to head (7fe592d).
Report is 3 commits behind head on master.

Files	Patch %	Lines
gno.land/pkg/gnoclient/client_txs.go	80.64%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1892      +/-   ##
==========================================
+ Coverage   47.74%   47.76%   +0.02%     
==========================================
  Files         393      393              
  Lines       61629    61664      +35     
==========================================
+ Hits        29424    29456      +32     
+ Misses      29734    29731       -3     
- Partials     2471     2477       +6     

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[zivkovicmilos]

Looks great 💯

[zivkovicmilos]

Pinging @gfanton to sign off and we can merge 🚀

[gfanton]

Looks good! I would add a usage example on how you can read and add a std.MemPackage. It can be tricky for a new user to figure out how to do that.