sqlite3: Add database and pragmas (#667)

I added the type definitions needed for my use case for the sqlite3 gem.
https://github.com/sparklemotion/sqlite3-ruby

gems/sqlite3/2.0/_test/test.rb

@@ -0,0 +1,27 @@
+# Write Ruby code to test the RBS.
+# It is type checked by `steep check` command.
+
+require "sqlite3"
+
+SQLite3::Database.new("test.db").execute("SELECT * FROM users").each do |row|
+  row[0] # Array
+end
+SQLite3::Database.new("test.db").execute("SELECT * FROM users") do |row|
+  row[0] # Array
+end
+
+SQLite3::Database.new("test.db", results_as_hash: true).execute("SELECT * FROM users").each do |row|
+  row['id'] # Hash
+end
+
+SQLite3::Database.new("test.db", results_as_hash: false).execute("SELECT * FROM users").each do |row|
+  row[0] # Array
+end
+
+SQLite3::Database.new("test.db") do |db|
+  db.busy_timeout = 5000
+end
+
+db = SQLite3::Database.new("test.db")
+db.execute("INSERT INTO users (name) VALUES ('john')")
+db.changes + 1

gems/sqlite3/2.0/database.rbs

@@ -0,0 +1,20 @@
+module SQLite3
+  type row_value_type = String | Integer | Float | nil
+  type result_as_hash = Hash[String, row_value_type]
+  type result_as_array = Array[row_value_type]
+
+  class Database[ResultType]
+    include Pragmas
+
+    def self.new: (String file, results_as_hash: true, **untyped) ?{ (Database[result_as_hash]) -> void } -> Database[result_as_hash]
+                | (String file, results_as_hash: false, **untyped) ?{ (Database[result_as_array]) -> void } -> Database[result_as_array]
+                | (String file, **untyped) ?{ (Database[result_as_array]) -> void } -> Database[result_as_array]
+
+    def execute: (String sql, *untyped) -> Array[ResultType]
+               | (String sql, *untyped) { (ResultType) -> void } -> void
+
+    def get_first_row: (String sql, *untyped) -> ResultType?
+
+    def changes: () -> Integer
+  end
+end

gems/sqlite3/2.0/pragmas.rbs

@@ -0,0 +1,5 @@
+module SQLite3
+  module Pragmas
+    def busy_timeout=: (Integer) -> void
+  end
+end