v10.15.0 and later do not support Node.js v14/v15 due to `performance` usage introduced in #715

[uncenter]

#715 breaks support for Node.js v14 and 15 (which are listed as supported versions) due to the introduction of code using performance.now() (1, 2), which is not available in the global context until Node.js v16 (previously it had to be imported manually with const { performance } = require('perf_hooks').

Discovered via 11ty/eleventy#3414.

[harttle]

Thanks @uncenter @vrugtehagel , the PR is merged. I'll try to create a node-version: 14 pipeline on GithubActions so it's checked.