Indent cdata filter with 4 spaces

It's original behavior.
https://github.com/haml/haml/blob/4.0.7/lib/haml/filters.rb#L259

Related to:
https://github.com/k0kubun/hamlit/pull/84

lib/hamlit/filters/cdata.rb

@@ -10,7 +10,7 @@ module Hamlit
       def compile_cdata(node)
         temple = [:multi]
         temple << [:static, "<![CDATA[\n".freeze]
-        compile_text!(temple, node, '  '.freeze)
+        compile_text!(temple, node, '    '.freeze)
         temple << [:static, "\n]]>".freeze]
         temple
       end

test/haml/filters_test.rb

@@ -226,7 +226,7 @@ class CSSFilterTest < Haml::TestCase
 end
 
 class CDATAFilterTest < Haml::TestCase
-  test "should wrap output in CDATA tag" do; skip
+  test "should wrap output in CDATA tag" do
     html = "<![CDATA[\n    foo\n]]>\n"
     haml = ":cdata\n  foo"
     assert_equal(html, render(haml))

test/hamlit/filters/cdata_test.rb

@@ -5,7 +5,7 @@ describe Hamlit::Filters do
     it 'renders cdata' do
       assert_render(<<-HTML.unindent, <<-HAML.unindent)
         <![CDATA[
-          foo bar
+            foo bar
         ]]>
       HTML
         :cdata
@@ -16,7 +16,7 @@ describe Hamlit::Filters do
     it 'parses string interpolation' do
       assert_render(<<-HTML.unindent, <<-HAML.unindent)
         <![CDATA[
-          foo <&> bar
+            foo <&> bar
         ]]>
       HTML
         :cdata