Documentation for `selectOnTab`'s default is out of date

[cpsievert]

The docs state that selectOnTab defaults to false, when in fact, it defaults to true.

https://github.com/selectize/selectize.js/blob/e3f2e0b4aa251375bc21b5fcd8ca7d374a921f08/docs/docs/usage.mdx#L86

https://github.com/selectize/selectize.js/blob/e3f2e0b4aa251375bc21b5fcd8ca7d374a921f08/src/defaults.js#L21

Note that the default was changed here https://github.com/selectize/selectize.js/issues/945, but as other users have brought up, selectOnTab: true isn't a great experience for keyboard-only users trying to navigate through a larger site (I'd be in support of reverting the default back to false).