docs: update features.md note about ESM imports in web workers

[vincerubinetti]

Description

Clarify section of docs that talk about ESM imports in web workers. Docs say that only Chrome is supported, but recently Safari and other browsers have added support, leaving only Firefox as unsupported. I also add a link to caniuse.com for up-to-date information.

Relevant StackOverflow answer with links to issue trackers for 3 major browsers:
https://stackoverflow.com/a/45578811/2180570

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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