Add SQLite info from README.

SQLite.md

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+# SQLite bindings
+
+There are some sqlite3 bindings in the directory natives/sqlite3 bundled with
+the janet source code. They serve mostly as a
+proof of concept external c library. To use, first compile the module with Make.
+
+```sh
+make natives
+```
+
+Next, enter the repl and create a database and a table.
+
+```
+janet:1:> (import natives/sqlite3 :as sql)
+nil
+janet:2:> (def db (sql/open "test.db"))
+<sqlite3.connection 0x5561A138C470>
+janet:3:> (sql/eval db `CREATE TABLE customers(id INTEGER PRIMARY KEY, name TEXT);`)
+@[]
+janet:4:> (sql/eval db `INSERT INTO customers VALUES(:id, :name);` {:name "John" :id 12345})
+@[]
+janet:5:> (sql/eval db `SELECT * FROM customers;`)
+@[{"id" 12345 "name" "John"}]
+```
+
+Finally, close the database connection when done with it.
+
+```
+janet:6:> (sql/close db)
+nil
+```