Add missing ExtractArchivePassword info.

ISHelp/isetup.xml

@@ -1660,6 +1660,11 @@ ExternalSize: 1048576; Flags: external
 </example>
 </param>
 
+<param name="ExtractArchivePassword">
+<p>Specifies the password of the archive. Please be aware that this password is stored in an unencrypted form in the resulting Setup file(s), even if you have enabled encryption (using the [Setup] section directive <tt>Encryption</tt>).</p>
+<p>This parameter is ignored if the <tt>extractarchive</tt> flag isn't also specified.</p>
+</param>
+
 <param name="Flags">
 <p>This parameter is a set of extra options. Multiple options may be used by separating them by spaces. The following options are supported:</p>
 
@@ -1707,7 +1712,7 @@ Instructs Setup to proceed to comparing time stamps (last write/modified time) i
 <p>This flag instructs Inno Setup not to statically compile the file specified by the <tt>Source</tt> parameter into the installation files, but instead to copy from an existing file on the distribution media or the user's system. See the <tt>Source</tt> parameter description for more information.</p>
 </flag>
 <flag name="extractarchive">
-<p>This flag instructs Inno Setup not to copy an existing archive file, but instead to extract it.</p>
+<p>This flag instructs Inno Setup not to copy an existing archive file, but instead to extract it. Optionally use the <tt>ExtractArchivePassword</tt> parameter to specify a password.</p>
 <p>The supported archive formats, beyond .7z, and the support for password-protected archives, depend on the <link topic="setup_archiveextraction">ArchiveExtraction</link> [Setup] section directive, that must not be set to <tt>basic</tt>.</p>
 <p>This flag must be combined with the <tt>external</tt> and <tt>ignoreversion</tt> flags, meaning it should only be used on files private to your application, <i>never</i> on shared system files.</p>
 <p>This flag is usually combined with the <tt>recursesubdirs</tt> and <tt>createallsubdirs</tt> flags.</p>