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.

example/env_demo.wren

@@ -0,0 +1,51 @@
+// retoor <retoor@molodetz.nl>
+
+import "env" for Environment
+
+System.print("=== Environment Module Demo ===\n")
+
+System.print("--- Reading Environment Variables ---")
+var home = Environment.get("HOME")
+var path = Environment.get("PATH")
+var user = Environment.get("USER")
+
+System.print("HOME: %(home)")
+System.print("USER: %(user)")
+System.print("PATH (first 80 chars): %(path[0...80])...")
+
+System.print("\n--- Reading Non-existent Variable ---")
+var missing = Environment.get("WREN_NONEXISTENT_VAR_12345")
+System.print("Missing variable: %(missing)")
+
+System.print("\n--- Setting Environment Variables ---")
+Environment.set("WREN_DEMO_VAR", "Hello from Wren!")
+var demoVar = Environment.get("WREN_DEMO_VAR")
+System.print("WREN_DEMO_VAR: %(demoVar)")
+
+Environment.set("WREN_DEMO_NUMBER", "42")
+System.print("WREN_DEMO_NUMBER: %(Environment.get("WREN_DEMO_NUMBER"))")
+
+System.print("\n--- Updating Environment Variables ---")
+Environment.set("WREN_DEMO_VAR", "Updated value")
+System.print("WREN_DEMO_VAR (updated): %(Environment.get("WREN_DEMO_VAR"))")
+
+System.print("\n--- Deleting Environment Variables ---")
+Environment.delete("WREN_DEMO_VAR")
+var afterDelete = Environment.get("WREN_DEMO_VAR")
+System.print("WREN_DEMO_VAR (after delete): %(afterDelete)")
+
+System.print("\n--- Listing All Environment Variables ---")
+var all = Environment.all
+System.print("Total environment variables: %(all.count)")
+
+System.print("\nFirst 10 environment variables:")
+var count = 0
+for (entry in all) {
+  if (count >= 10) break
+  var value = entry.value
+  if (value.count > 40) value = value[0...40] + "..."
+  System.print("  %(entry.key) = %(value)")
+  count = count + 1
+}
+
+Environment.delete("WREN_DEMO_NUMBER")