activestorage: Add ActiveStorage::Current

refs:

* https://github.com/rails/rails/blob/v6.0.6.1/activestorage/app/models/active_storage/current.rb
* https://github.com/rails/rails/blob/v7.0.8.6/activestorage/app/models/active_storage/current.rb
    * `#url_options` has been added and `#host` has been deprecated

gems/activestorage/6.0/app/models/active_storage/current.rbs

@@ -0,0 +1,8 @@
+module ActiveStorage
+  class Current < ActiveSupport::CurrentAttributes
+    def self.host: () -> String
+    def self.host=: (String) -> String
+    def host: () -> String
+    def host=: (String) -> String
+  end
+end

gems/activestorage/6.1/app/models/active_storage/current.rbs

@@ -0,0 +1 @@
+../../../../6.0/app/models/active_storage/current.rbs

gems/activestorage/7.0/app/models/active_storage/current.rbs

@@ -0,0 +1,8 @@
+module ActiveStorage
+  class Current < ActiveSupport::CurrentAttributes
+    def self.url_options: () -> Hasy[Symbol, untyped]
+    def self.url_options=: (Hasy[Symbol, untyped]) -> Hasy[Symbol, untyped]
+    def url_options: () -> Hasy[Symbol, untyped]
+    def url_options=: (Hasy[Symbol, untyped]) -> Hasy[Symbol, untyped]
+  end
+end