Spelling/syntax suggestions

“Add you accordion content here.” should be:
Add your accordion content here.

“New Accordions” (2 places) should be:
New Accordion

“Simply copy these shortcode and user under content” should be
Simply copy these shortcodes and user under content

“This is useful when use collapsible.” should be:
This is useful when collapsible is true.

“Keep expanded others” should be:
Keep others expanded