docs💥: revamp extension guide (#1494)

* docs💥: revamp extension guide

* docs: update extension example

* docs: oops, forgot a word

Co-authored-by: Max <maxyolo01.ytb@gmail.com>
Signed-off-by: Astrea <25420078+AstreaTSS@users.noreply.github.com>

* docs: add section for loading all extensions in folder

* docs: turns out ipy can load multi exts in one file

* docs: lots of wording adjustments

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Signed-off-by: Astrea <25420078+AstreaTSS@users.noreply.github.com>
Co-authored-by: Max <maxyolo01.ytb@gmail.com>
Co-authored-by: LordOfPolls <dev@lordofpolls.com>

Author: 3 people