netsurf: move to public only API

And add some Node APIs:
- getters: firstChild, lastChild, nextSibling, previoussibling,
parentNode, parentElement, nodeName, nodeType, ownerDocument,
isConnected
- getters/setters: nodeValue, textContent
- methods: appendChild

And some test comptime optimizations on Document

Signed-off-by: Francis Bouvier <francis.bouvier@gmail.com>

src/dom/comment.zig

@@ -0,0 +1,9 @@
+const parser = @import("../netsurf.zig");
+
+const CharacterData = @import("character_data.zig").CharacterData;
+
+pub const Comment = struct {
+    pub const Self = parser.Comment;
+    pub const prototype = *CharacterData;
+    pub const mem_guarantied = true;
+};