add 'asserts' library

res/modules/internal/asserts.lua

@@ -0,0 +1,10 @@
+local this = {}
+
+function this.equals(expected, fact)
+    assert(fact == expected, string.format(
+        "(fact == expected) assertion failed\n  Expected: %s\n  Fact:     %s",
+        expected, fact
+    ))
+end
+
+return this

res/scripts/stdlib.lua

@@ -174,6 +174,7 @@ if enable_experimental then
     require "core:internal/maths_inline"
 end
 
+asserts = require "core:internal/asserts"
 events = require "core:internal/events"
 
 function pack.unload(prefix)