Use nord8 for Markdown link titles

The color of Markdown link titles was previously highlighted with
`nord14` and has been changed to `nord8` in order to match Nord's
Markdown syntax styles.

GH-79

resources/themes/nord.xml

@@ -1293,7 +1293,7 @@
     </option>
     <option name="MARKDOWN_LINK_TEXT">
       <value>
-        <option name="FOREGROUND" value="a3be8c" />
+        <option name="FOREGROUND" value="88c0d0" />
         <option name="EFFECT_TYPE" value="1" />
       </value>
     </option>