Use performance now in tokenizeString instead of the raw Date.now()

[Jacob-Roberts]

This function is being exported and used downstream in some projects that rely on next.js 16's cache components.

This doesn't allow using Date.now() and requires the use of performance.now() instead.

Since this file already imports the helper for using performanceNow() let's move over to use that.

This closes https://github.com/code-hike/lighter/issues/51.

Also, I've upstreamed this request: https://github.com/microsoft/vscode-textmate/pull/258

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[Jacob-Roberts]

As a temporary workaround, I've published @autovation/bright which has this change