Change `.tids` file extension to `.multids`

Hopefully less confusing

boot/boot.js

@@ -1502,7 +1502,7 @@ $tw.boot.startup = function(options) {
 	// Add file extension information
 	$tw.utils.registerFileType("text/vnd.tiddlywiki","utf8",".tid");
 	$tw.utils.registerFileType("application/x-tiddler","utf8",".tid");
-	$tw.utils.registerFileType("application/x-tiddlers","utf8",".tids");
+	$tw.utils.registerFileType("application/x-tiddlers","utf8",".multids");
 	$tw.utils.registerFileType("application/x-tiddler-html-div","utf8",".tiddler");
 	$tw.utils.registerFileType("text/vnd.tiddlywiki2-recipe","utf8",".recipe");
 	$tw.utils.registerFileType("text/plain","utf8",".txt");

editions/tw5.com/tiddlers/howtos/How to create a translation for TiddlyWiki.tid

@@ -26,7 +26,7 @@ Quick and dirty instructions:
 # Run `./qbld.sh` to build TiddlyWiki
 # Open the TiddlyWiki file at `/MyTranslation/jermolene.github.com/index.html`
 # You should see your translation listed in the control panel, but the text of the translation will still be in British English
-# Edit the `.tid` and `.tids` files in your language folder to translate the English text
+# Edit the `.tid` and `.multids` files in your language folder to translate the English text
 
 Content of `plugin.info` for Joe Bloggs' Welsh translation: