Fix a typo in the manual

Closes #5581

Author: marijnh

doc/manual.html

@@ -2321,7 +2321,7 @@ <h2 id="addons">Addons</h2>
       a <code>{line, ch}</code> object, or can be left off to default
       to the start of the document. <code>options</code> is an
       optional object, which can contain the property `caseFold:
-      false` to disable case folding when mathing a string, or the
+      false` to disable case folding when matching a string, or the
       property `multiline: disable` to disable multi-line matching for
       regular expressions (which may help performance). A search
       cursor has the following methods: