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/sqlite/sqlite.wren

@@ -0,0 +1,27 @@
+// retoor <retoor@molodetz.nl>
+
+import "sqlite" for Database
+
+var db = Database.memory()
+System.print(db is Database) // expect: true
+
+db.execute("CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT, age INTEGER)")
+
+db.execute("INSERT INTO users (name, age) VALUES (?, ?)", ["Alice", 30])
+System.print(db.lastInsertId) // expect: 1
+System.print(db.changes) // expect: 1
+
+db.execute("INSERT INTO users (name, age) VALUES (?, ?)", ["Bob", 25])
+System.print(db.lastInsertId) // expect: 2
+
+var rows = db.query("SELECT * FROM users ORDER BY id")
+System.print(rows.count) // expect: 2
+System.print(rows[0]["name"]) // expect: Alice
+System.print(rows[0]["age"]) // expect: 30
+System.print(rows[1]["name"]) // expect: Bob
+
+var filtered = db.query("SELECT * FROM users WHERE age > ?", [26])
+System.print(filtered.count) // expect: 1
+System.print(filtered[0]["name"]) // expect: Alice
+
+db.close()