feat: add cJSON and SQLite amalgamation source files under deps/

Add the cJSON library (cJSON.c, cJSON.h) and SQLite amalgamation
(sqlite3.c, sqlite3.h, sqlite3ext.h, shell.c) as vendored dependencies
in the deps/ directory for use by the project build system.

test/jinja/set.wren

@@ -0,0 +1,15 @@
+// retoor <retoor@molodetz.nl>
+
+import "jinja" for Environment, DictLoader
+
+var env = Environment.new(DictLoader.new({
+  "set_simple": "{\% set x = 5 \%}{{ x }}",
+  "set_expr": "{\% set y = 2 + 3 \%}{{ y }}",
+  "set_from_var": "{\% set z = a + b \%}{{ z }}",
+  "set_string": "{\% set msg = \"hello\" \%}{{ msg|upper }}"
+}))
+
+System.print(env.getTemplate("set_simple").render({})) // expect: 5
+System.print(env.getTemplate("set_expr").render({})) // expect: 5
+System.print(env.getTemplate("set_from_var").render({"a": 10, "b": 20})) // expect: 30
+System.print(env.getTemplate("set_string").render({})) // expect: HELLO