Add .tc-small-gap (+left / right) and .tc-big-gap... (#4923)

(+left / right) classes that define margins of .5em / 1em

themes/tiddlywiki/vanilla/base.tid

@@ -2761,3 +2761,33 @@ select {
 .tc-fill-background {
 	fill: <<colour background>>;
 }
+
+/*
+** Other utility classes
+*/
+
+.tc-small-gap {
+	margin-left: .5em;
+	margin-right: .5em;
+}
+
+.tc-small-gap-left {
+	margin-left: .5em;
+}
+
+.tc-small-gap-right {
+	margin-right: .5em;
+}
+
+.tc-big-gap {
+	margin-left: 1em;
+	margin-right: 1em;
+}
+
+.tc-big-gap-left {
+	margin-left: 1em;
+}
+
+.tc-big-gap-right {
+	margin-right: 1em;
+}