Add playsInline to docs

Added to the list of allowed attributes in the documentation.

Author: reaperhulk

docs/docs/ref-04-tags-and-attributes.md

@@ -65,10 +65,10 @@ formNoValidate formTarget frameBorder headers height hidden high href hrefLang
 htmlFor httpEquiv icon id inputMode integrity is keyParams keyType kind label
 lang list loop low manifest marginHeight marginWidth max maxLength media
 mediaGroup method min minLength multiple muted name noValidate nonce open
-optimum pattern placeholder poster preload profile radioGroup readOnly rel
-required reversed role rowSpan rows sandbox scope scoped scrolling seamless
-selected shape size sizes span spellCheck src srcDoc srcLang srcSet start step
-style summary tabIndex target title type useMap value width wmode wrap
+optimum pattern placeholder playsInline poster preload profile radioGroup 
+readOnly rel required reversed role rowSpan rows sandbox scope scoped scrolling 
+seamless selected shape size sizes span spellCheck src srcDoc srcLang srcSet 
+start step style summary tabIndex target title type useMap value width wmode wrap
 ```
 
 These RDFa attributes are supported (several RDFa attributes overlap with standard HTML attributes and thus are excluded from this list):