chore: adds ohmyzsh plugin for gaiad

[tokamak-git]

Description

Closes: #1331

https://github.com/cosmos/gaia/issues/1331

adds ohmyzsh completion script with instructions for gaiad

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Author Checklist

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• [x] Included the correct type prefix in the PR title
• [x] Targeted the correct branch (see PR Targeting)
• [x] Provided a link to the relevant issue or specification
• [x] Reviewed "Files changed" and left comments if necessary
• [x] Confirmed all CI checks have passed

Reviewers Checklist

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• [ ] Confirmed the correct type prefix in the PR title
• [ ] Confirmed all author checklist items have been addressed
• [ ] Confirmed that this PR does not change production code