Add example for all

Author: erichaney

examples/all.janet

@@ -0,0 +1,8 @@
+(all pos? [1 2 3]) # -> true
+(all pos? [1 2 -3]) # -> false
+
+(all pos? []) # -> true
+(all neg? []) # -> true
+
+(all truthy? [1 2 3]) # -> true
+(all truthy? [1 2 nil]) # -> false