Minify area[shape] attr; simplify NS code

gen/build/attrs.js

@@ -94,6 +94,10 @@ const defaultAttributeValues = {
     tags: ['html:table'],
     defaultValue: 'none',
   }],
+  'shape': [{
+    tags: ['html:area'],
+    defaultValue: 'rect',
+  }],
   'span': [{
     tags: ['html:col', 'html:colgroup'],
     defaultValue: '1',

src/unit/tag.rs

@@ -194,7 +194,7 @@ pub fn process_tag(proc: &mut Processor, ns: Namespace, mut prev_sibling_closing
         return Ok(MaybeClosingTag(None));
     };
 
-    let child_ns = if ns != Namespace::Svg && proc[tag_name].eq(b"svg") {
+    let child_ns = if proc[tag_name].eq(b"svg") {
         Namespace::Svg
     } else {
         ns