chore/esm stylelint config

[thescientist13]

Related Issue

Carried on from https://github.com/AnalogStudiosRI/www.blissfestri.com/pull/131

Summary of Changes

1. Upgrade to Stylelint 16 with ESM config support

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It looks like the current stylelint-a11y package has been [unmaintained for a bit](), and while there are forks, it doesn't seem like they are able to support Stylelint 16

• https://github.com/YozhikM/stylelint-a11y/issues/75
• https://github.com/developer-stylechain/stylelint-a11y/issues/4
• https://github.com/mechanical-ink/stylelint-a11y
• https://github.com/stylelint/stylelint/issues/6212