Allow to add error details with Logger#add_error

lib/rackstash/logger.rb

@@ -364,6 +364,7 @@ module Rackstash
     def add_exception(exception, force: true)
       buffer.add_exception(exception, force: force)
     end
+    alias add_error add_exception
 
     # Create a new {Buffer} and put it on the {BufferStack} for the current
     # Thread. Until it is poped again with {#pop_buffer}, all newly logged

spec/rackstash/logger_spec.rb

@@ -483,6 +483,10 @@ describe Rackstash::Logger do
       expect(Rackstash::Buffer.instance_method(:add_exception).parameters)
         .to eql logger.method(:add_exception).parameters
     end
+
+    it 'can be called as #add_error' do
+      expect(logger.method(:add_error)).to eql logger.method(:add_exception)
+    end
   end
 
   describe '#push_buffer' do