[.mailcap] Seems that filenames with apostrohes and brackets are not handled properly

Compile: gcc -o echo.exe echo.c

contrib/audio/.mailcap

@@ -1 +1 @@
-audio/*; echo '{"command":["loadfile","%s","append-play"]}' | socat - /tmp/mpv.sock 2> /dev/null > /dev/null
+audio/*; echo.exe %s | socat - /tmp/mpv.sock 2> /dev/null > /dev/null

contrib/audio/echo.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+int
+main(int argc, char **argv)
+{
+    printf("{\"command\":[\"loadfile\",\"%s\",\"append-play\"]}\n", argv[1]);
+    return 0;
+}