Update release notes and thanks file

RELEASE_NOTES.md

@@ -60,6 +60,7 @@ Behaviour
 * Search results link open in the same window, which is consistent with
   internet search engines
 * Comments section message changes when user toggles it
+* Fixed: Clicking Search button in 404.html does not trigger search
 
 Version 1.3
 ===========

THANKS.md

@@ -7,6 +7,13 @@ Thanks to
 1. He [helped](https://github.com/talha131/pelican-elegant/issues/81) in
    resolving a performance issue
 
+[Andre](https://github.com/andreburgaud)
+----------------------------------------
+
+1. He [reported and submitted a
+   patch](https://github.com/talha131/pelican-elegant/issues/108) to fix a bug
+   in 404.html
+
 [brechtm](https://github.com/brechtm)
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