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/includes.wren

@@ -0,0 +1,14 @@
+// retoor <retoor@molodetz.nl>
+
+import "jinja" for Environment, DictLoader
+
+var env = Environment.new(DictLoader.new({
+  "header": "<header>{{ title }}</header>",
+  "main": "{\% include \"header\" \%}content",
+  "with_ctx": "{\% include \"header\" with context \%}",
+  "without_ctx": "{\% include \"header\" without context \%}"
+}))
+
+System.print(env.getTemplate("main").render({"title": "Hello"})) // expect: <header>Hello</header>content
+System.print(env.getTemplate("with_ctx").render({"title": "Test"})) // expect: <header>Test</header>
+System.print(env.getTemplate("without_ctx").render({"title": "Test"})) // expect: <header></header>