Add ECMAScript version to Falafel/Acorn.js config

[camdecoster]

Description

Add config option to Falafel calls (which gets passed to Acorn) to allow for parsing of the newest ECMAScript syntax.

Changes

• Updates (or adds) Falafel config to specify the latest ECMAScript version

Testing

If CI passes, that should be proof enough that this change didn't break anything.

Notes

• We recently specified an updated version of Acorn.js to be used as a dependency of the Falafel library
• The newer version of Acorn.js includes a warning message that specifying ecmaVersion is now required:

  Since Acorn 8.0.0, options.ecmaVersion is required. Defaulting to 2020, but this will stop working in the future.

• Modern ECMAScript syntax can sometimes cause Acorn.js to fail because it's not parsing the proper version of ECMAScript (I saw it with the logical OR operator: ||=)
• By using an ecmaScript value of "latest" with Acorn.js, we should be covered now and in the future if we start using other modern syntax