chore: Initialize wallet package

[FrederikBolding]

Explanation

Initialize the wallet package, which will eventually contain shared initialization code for the MetaMask clients.

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Low Risk
Low risk: this PR primarily scaffolds a new package and wires it into repo tooling (TypeScript refs, docs, ownership) with only placeholder code and a basic unit test.

Overview
Adds a new @metamask/wallet workspace package scaffold (build/test/docs configs, licensing/changelog/readme) with a placeholder greeter export and a simple Jest test.

Wires the new package into monorepo infrastructure by updating root tsconfig.json/tsconfig.build.json references, README.md package list/dependency graph, CODEOWNERS/teams.json ownership mapping, and yarn.lock workspace entry.

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[Gudahtt]

LGTM!

[mcmire]

LGTM.

[mcmire]

This reminds me, I really should update the create-package tool to include both licenses...