Upgrade TypeScript to v6

[caugner]

Dependabot opened PRs to upgrade TypeScript to v6, but npm ci is failing where typescript-eslint is used:

• chore(deps-dev): bump typescript from 5.9.3 to 6.0.2 browser-compat-data#29329
• chore(deps-dev): bump typescript from 5.9.3 to 6.0.2 dex#271
• chore(deps-dev): bump typescript from 5.9.3 to 6.0.2 in /cloud-function dex#272
• chore(deps-dev): bump typescript from 5.9.3 to 6.0.2 #1416
• chore(deps-dev): bump typescript from 5.9.3 to 6.0.2 mdn-http-observatory#472

Blocked by:

• TypeScript 6 Support typescript-eslint/typescript-eslint#12123

[caugner]

TS6 support dropped:

• chore(deps-dev): bump typescript-eslint from 8.57.2 to 8.58.0 in the npm-dev group dex#283

[caugner]

Important change:

In TypeScript 6.0, the default types value will be [] (an empty array). This change prevents projects from unintentionally pulling in hundreds or even thousands of unneeded declaration files at build time. Many projects we’ve looked at have improved their build time anywhere from 20-50% just by setting types appropriately.

This will affect many projects. You will likely need to add "types": ["node"] or a few others:

See: https://www.typescriptlang.org/docs/handbook/release-notes/typescript-6-0.html#types-now-defaults-to-