Use Jinja2, start to support sprites

pytools/BUILD

@@ -2,9 +2,10 @@ load("@pytools_deps//:requirements.bzl", "requirement")
 
 py_binary(
     name = "font",
-    srcs = ["font.py"],
+    srcs = ["font.py", "shared.py"],
     deps = [
         requirement("pillow"),
+        requirement("Jinja2"),
     ],
     visibility = ["//visibility:public"],
 )