Make highlighting effective for code-formatted text (#1215)

Currently the background color of code tag is opaque, therefore the
highlighting will be covered by the code-formatted text. Let's
introduce transparency to code tag style when it's placed under
mark tag so that highlighting is effective in this case.

asset/css/markbind.css

@@ -11,6 +11,10 @@ code {
     word-break: normal;
 }
 
+mark code {
+    background: #ffffffd4;
+}
+
 pre.hljs > code {
     background: none;
 }

test/functional/test_site/expected/markbind/css/markbind.css

@@ -11,6 +11,10 @@ code {
     word-break: normal;
 }
 
+mark code {
+    background: #ffffffd4;
+}
+
 pre.hljs > code {
     background: none;
 }

test/functional/test_site_algolia_plugin/expected/markbind/css/markbind.css

@@ -11,6 +11,10 @@ code {
     word-break: normal;
 }
 
+mark code {
+    background: #ffffffd4;
+}
+
 pre.hljs > code {
     background: none;
 }

test/functional/test_site_convert/expected/markbind/css/markbind.css

@@ -11,6 +11,10 @@ code {
     word-break: normal;
 }
 
+mark code {
+    background: #ffffffd4;
+}
+
 pre.hljs > code {
     background: none;
 }

test/functional/test_site_expressive_layout/expected/markbind/css/markbind.css

@@ -11,6 +11,10 @@ code {
     word-break: normal;
 }
 
+mark code {
+    background: #ffffffd4;
+}
+
 pre.hljs > code {
     background: none;
 }

test/functional/test_site_special_tags/expected/markbind/css/markbind.css

@@ -11,6 +11,10 @@ code {
     word-break: normal;
 }
 
+mark code {
+    background: #ffffffd4;
+}
+
 pre.hljs > code {
     background: none;
 }

test/functional/test_site_templates/test_default/expected/markbind/css/markbind.css

@@ -11,6 +11,10 @@ code {
     word-break: normal;
 }
 
+mark code {
+    background: #ffffffd4;
+}
+
 pre.hljs > code {
     background: none;
 }

test/functional/test_site_templates/test_minimal/expected/markbind/css/markbind.css

@@ -11,6 +11,10 @@ code {
     word-break: normal;
 }
 
+mark code {
+    background: #ffffffd4;
+}
+
 pre.hljs > code {
     background: none;
 }