Fix decleration to declaration in helpers/html_helper.rst

Co-authored-by: Denny Septian Panggabean <97607754+ddevsr@users.noreply.github.com>

Author: obozdag

user_guide_src/source/helpers/html_helper.rst

@@ -342,7 +342,7 @@ The following functions are available:
 .. php:function:: doctype([$type = 'html5'])
 
     :param  string  $type: Doctype name
-    :returns:   An HTML DocType decleration
+    :returns:   An HTML DocType declaration
     :rtype: string
 
     Helps you generate document type declarations (DTD's). HTML 5