Add missing headers to Active Support docs [ci-skip]

 Having a h1 heading will improve SEO and makes things look more consistent.

Author: p8

activesupport/lib/active_support/actionable_error.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 module ActiveSupport
+  # = Actionable Errors
+  #
   # Actionable errors lets you define actions to resolve an error.
   #
   # To make an error actionable, include the <tt>ActiveSupport::ActionableError</tt>

activesupport/lib/active_support/array_inquirer.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 module ActiveSupport
+  # = \Array Inquirer
+  #
   # Wrapping an array in an +ArrayInquirer+ gives a friendlier way to check
   # its string-like contents:
   #

activesupport/lib/active_support/backtrace_cleaner.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 module ActiveSupport
+  # = Backtrace Cleaner
+  #
   # Backtraces often include many lines that are not relevant for the context
   # under review. This makes it hard to find the signal amongst the backtrace
   # noise, and adds debugging time. With a BacktraceCleaner, filters and

activesupport/lib/active_support/benchmarkable.rb

@@ -4,6 +4,7 @@
 require "active_support/core_ext/hash/keys"
 
 module ActiveSupport
+  # = \Benchmarkable
   module Benchmarkable
     # Allows you to measure the execution time of a block in a template and
     # records the result to the log. Wrap this block around expensive operations

activesupport/lib/active_support/cache.rb

@@ -130,6 +130,8 @@ def retrieve_store_class(store)
         end
     end
 
+    # = Active Support \Cache \Store
+    #
     # An abstract cache store class. There are multiple cache store
     # implementations, each having its own additional features. See the classes
     # under the ActiveSupport::Cache module, e.g.

activesupport/lib/active_support/cache/file_store.rb

@@ -6,6 +6,8 @@
 
 module ActiveSupport
   module Cache
+    # = \File \Cache \Store
+    #
     # A cache store implementation which stores everything on the filesystem.
     class FileStore < Store
       attr_reader :cache_path

activesupport/lib/active_support/cache/mem_cache_store.rb

@@ -15,6 +15,8 @@
 
 module ActiveSupport
   module Cache
+    # = Memcached \Cache \Store
+    #
     # A cache store implementation which stores data in Memcached:
     # https://memcached.org
     #

activesupport/lib/active_support/cache/memory_store.rb

@@ -4,6 +4,8 @@
 
 module ActiveSupport
   module Cache
+    # = Memory \Cache \Store
+    #
     # A cache store implementation which stores everything into memory in the
     # same process. If you're running multiple Ruby on Rails server processes
     # (which is the case if you're using Phusion Passenger or puma clustered mode),

activesupport/lib/active_support/cache/null_store.rb

@@ -2,6 +2,8 @@
 
 module ActiveSupport
   module Cache
+    # = Null \Cache \Store
+    #
     # A cache store implementation which doesn't actually store anything. Useful in
     # development and test environments where you don't want caching turned on but
     # need to go through the caching interface.

activesupport/lib/active_support/cache/redis_cache_store.rb

@@ -15,7 +15,7 @@
 
 module ActiveSupport
   module Cache
-    # Redis cache store.
+    # = Redis \Cache \Store
     #
     # Deployment note: Take care to use a *dedicated Redis cache* rather
     # than pointing this at your existing Redis server. It won't cope well