Add trailing slash to URL

Author: microbit-mark

spec/index.md

@@ -3,7 +3,7 @@ layout: page
 title: Universal Hex Format Specification
 heading: Universal Hex Format Specification
 description: Specification for the micro:bit Universal Hex Format
-permalink: /software/spec-universal-hex
+permalink: /software/spec-universal-hex/
 ref: spec-universal-hex
 lang: en
 ---