Add rbs for mysql2-0.5 (#563)

https://github.com/brianmario/mysql2

gems/mysql2/0.5/_test/test.rb

@@ -0,0 +1,22 @@
+require "mysql2"
+
+client = Mysql2::Client.new(
+  host: '127.0.0.1',
+  port: 3306,
+  username: 'root',
+  password: 'password',
+  database: 'foo',
+  symbolize_keys: true,
+  cast_booleans: true,
+  reconnect: true,
+)
+
+client.query("SELECT * FROM users").each do |row|
+  raise unless row.is_a?(Hash)
+  row[:id]
+end
+
+client.query("SELECT id FROM users", as: :array).each do |row|
+  raise unless row.is_a?(Array)
+  row[0]
+end

gems/mysql2/0.5/client.rbs

@@ -0,0 +1,42 @@
+module Mysql2
+  class Client
+    self.@default_query_options: untyped
+
+    @read_timeout: untyped
+
+    @query_options: untyped
+
+    attr_reader query_options: untyped
+
+    attr_reader read_timeout: untyped
+
+    def self.default_query_options: () -> untyped
+
+    def initialize: (Hash[(String | Symbol), untyped] opts) -> void
+
+    def parse_ssl_mode: (untyped mode) -> untyped
+
+    def parse_flags_array: (untyped flags, ?::Integer initial) -> untyped
+
+    # Find any default system CA paths to handle system roots
+    # by default if stricter validation is requested and no
+    # path is provide.
+    def find_default_ca_path: () -> untyped
+
+    # Set default program_name in performance_schema.session_connect_attrs
+    # and performance_schema.session_account_connect_attrs
+    def parse_connect_attrs: (untyped conn_attrs) -> (::Hash[untyped, untyped] | untyped)
+
+    def query: (String sql, ?::Hash[untyped, untyped] options) -> Mysql2::result
+
+    def query_info: () -> (::Hash[untyped, untyped] | untyped)
+
+    def info: () -> untyped
+
+    def last_id: () -> Integer
+
+    private
+
+    def self.local_offset: () -> untyped
+  end
+end

gems/mysql2/0.5/result.rbs

@@ -0,0 +1,20 @@
+module Mysql2
+  type row_value_type = String | Integer | nil
+  type result = ResultAsHash | ResultAsArray
+
+  class ResultAsHash
+    attr_reader server_flags: untyped
+
+    include Enumerable[Hash[Symbol, row_value_type]]
+
+    def each: () { (Hash[Symbol, row_value_type]) -> void } -> void
+  end
+
+  class ResultAsArray
+    attr_reader server_flags: untyped
+
+    include Enumerable[Array[row_value_type]]
+
+    def each: () { (Array[row_value_type]) -> void } -> void
+  end
+end