Add wiki_preprocess hook and documentation

Zotlabs/Lib/NativeWikiPage.php

@@ -619,7 +619,7 @@ class NativeWikiPage {
 			$s = str_replace('[observer.webname]', '', $s);
 			$s = str_replace('[observer.photo]', '', $s);
 		}
-	
+
 		return $s;
 	}
 	

Zotlabs/Module/Wiki.php

@@ -331,6 +331,10 @@ class Wiki extends Controller {
 				        $sampleContent = t('New page');
 
 				    $content = (($p['content'] == '') ? $sampleContent : $p['content']);
+
+				    $hookinfo = ['content' => $content, 'mimetype' => $mimeType];
+				    call_hooks('wiki_preprocess',$hookinfo);
+				    $content = $hookinfo['content'];
     
 				    // Render the Markdown-formatted page content in HTML
 				    if($mimeType == 'text/bbcode') {

doc/hook/wiki_preprocess.bb

@@ -0,0 +1,11 @@
+[h3]wiki_preprocess[/h3]
+        
+Called before markdown/bbcode processors are run for wiki pages
+
+Passed parameter array:
+
+	'content' => wiki page content
+	'mimetype'   => page mimetype
+
+
+see: Zotlabs/Module/Wiki.php

doc/hooklist.bb

@@ -625,6 +625,9 @@ Hooks allow plugins/addons to "hook into" the code at many points and alter the
 [zrl=[baseurl]/help/hook/well_known]well_known[/zrl]
 	Called when accessing the '.well-known' special site addresses
 
+[zrl=[baseurl]/help/hook/wiki_preprocess]wiki_preprocess[/zrl]
+	Called before markdown/bbcode processors are run for wiki pages
+
 [zrl=[baseurl]/help/hook/zot_best_algorithm]zot_best_algorithm[/zrl]
 	Called when negotiating crypto algorithms with remote sites