Add deep access

Signed-off-by: Marcel Müller <neikos@neikos.email>

tests/cases/deep_access.4-output.snap

@@ -0,0 +1,11 @@
+---
+source: tests/file_tests.rs
+expression: output
+info:
+  input: "{{ if world?.active }}\nHello {{= world.name }}\n{{ end }}\n\n{{ if world?.foo?.bar?.active }}\n    Weird!\n{{ else }}\n    Deep access is working :)\n{{ end }}"
+  context:
+    world:
+      active: true
+      name: World!
+---
+"\nHello World!\n\n\n\n    Deep access is working :)\n"