feat: added money-account-balance-service to root tsconfig files

[Matt561]

Explanation

Add @metamask/money-account-balance-service to the root tsconfig.json and tsconfig.build.json files.

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
Only updates TypeScript project references and changelog; no runtime or business-logic behavior changes.

Overview
Adds packages/money-account-balance-service to the root tsconfig.json and tsconfig.build.json project references, making it included in repo-wide TypeScript linting/editor tooling and in the aggregated build.

Updates packages/money-account-balance-service/CHANGELOG.md under Unreleased to document the new root tsconfig inclusion.

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[mcmire]

@Matt561 Should we also include an entry in the changelog for the package, since this fixes the package so it's usable now?

[Matt561]

@Matt561 Should we also include an entry in the changelog for the package, since this fixes the package so it's usable now?

Good idea. I've updated the changelog 👍

[mcmire]

Tested by running yarn build. The dist directory in money-account-balance-service now exists and has the correct files. LGTM.