Declare dynamic methods

Two main cases:

- `attr_*` needs `@dynamic`: soutaro/steep#1036
- three `define_method` because of the `RUBY_VERSION` condition

lib/graft/callback.rb

@@ -2,6 +2,7 @@
 
 module Graft
   class Callback
+    # @dynamic name
     attr_reader :name
 
     # NOTE: opts is not used in the current implementation
@@ -12,6 +13,7 @@ def initialize(name = nil, opts = {}, &block)
       @enabled = true
     end
 
+    # @dynamic call
     # Using `define_method` instead of `def` as the latter trips up static type checking
     if RUBY_VERSION < "3.0"
       define_method :call do |*args, &block|

lib/graft/hook.rb

@@ -44,6 +44,7 @@ def self.ignore
       Thread.current[:hook_entered] = false
     end
 
+    # @dynamic point, stack
     attr_reader :point, :stack
 
     # NOTE: Push logic upward ClassMethods
@@ -117,6 +118,7 @@ def uninstall
     end
 
     class << self
+      # @dynamic wrapper
       # Using `define_method` instead of `def` as the latter trips up static type checking
       if RUBY_VERSION < "3.0"
         define_method :wrapper do |hook|

lib/graft/hook_point.rb

@@ -10,6 +10,7 @@ def initialize(key)
       @key = key
     end
 
+    # @dynamic key
     attr_reader :key
 
     def inspect
@@ -62,6 +63,7 @@ def strategy_module(strategy)
       end
     end
 
+    # @dynamic klass_name, method_kind, method_name
     attr_reader :klass_name, :method_kind, :method_name
 
     def initialize(hook_point, strategy = DEFAULT_STRATEGY)
@@ -396,6 +398,7 @@ def unchain(suffix)
         end
       end
 
+      # @dynamic apply
       # Using `define_method` instead of `def` as the latter trips up static type checking
       if RUBY_VERSION < "3.0"
         define_method :apply do |obj, suffix, *args, &block|