FU::Util: Add brotli_compress() and use it for FU output compression

Seems to compresses and perform better than libdeflate at level 6, so
certainly worth using.

FU.xs

@@ -126,6 +126,10 @@ void gzip_compress(IV level, SV *in)
   CODE:
     ST(0) = fugz_compress(aTHX_ level, in);
 
+void brotli_compress(IV level, SV *in)
+  CODE:
+    ST(0) = fubr_compress(aTHX_ level, in);
+
 void fdpass_send(int socket, int fd, SV *data)
   CODE:
     STRLEN buflen;