Add ignore rules for Linux ARM exports

Since Processing version 3.0.1 you can compile Linux ARM versions of your Processing sketch, distinct from the regular 32 and 64 bit Linux exports.

Processing.gitignore

@@ -1,5 +1,7 @@
 .DS_Store
 applet
+application.linux-arm64
+application.linux-armv6hf
 application.linux32
 application.linux64
 application.windows32