Fix #80671: Update mb_convert_encoding

* Update `mb_convert_encoding` changelog
Now throws `ValueError` if either $to_encoding or $from_encoding
are passed an invalid encoding, this change was introduced in PHP 8.0
* Add errors section to `mb_convert_encoding`

Co-authored-by: George Peter Banyard <[email protected]>

Closes GH-582.

Author: thinkverse

reference/mbstring/functions/mb-convert-encoding.xml

@@ -70,6 +70,16 @@
   </para>
  </refsect1>
 
+ <refsect1 role="errors">
+  &reftitle.errors;
+  <para>
+   As of PHP 8.0.0, a <classname>ValueError</classname> is thrown if the
+   value of <parameter>to_encoding</parameter> or 
+   <parameter>from_encoding</parameter> is an invalid encoding.
+   Prior to PHP 8.0.0, a <constant>E_WARNING</constant> was emitted instead.
+  </para>
+ </refsect1>
+
  <refsect1 role="changelog">
   &reftitle.changelog;
   <informaltable>
@@ -81,6 +91,22 @@
      </row>
     </thead>
     <tbody>
+     <row>
+      <entry>8.0.0</entry>
+      <entry>
+       <function>mb_convert_encoding</function> will now throw a
+       <classname>ValueError</classname> when 
+       <parameter>to_encoding</parameter> is passed an invalid encoding.
+      </entry>
+     </row>
+     <row>
+      <entry>8.0.0</entry>
+      <entry>
+       <function>mb_convert_encoding</function> will now throw a
+       <classname>ValueError</classname> when 
+       <parameter>from_encoding</parameter> is passed an invalid encoding.
+      </entry>
+     </row>
      <row>
       <entry>8.0.0</entry>
       <entry>