chore(README): Update documentation for the special field (#534)

One part of the README still uses the old separate static,
stringifier, and inherit fields. In other places it is stated that the
special field is null in the default case, when in fact the special
field is set to the empty string.

Closes: #533

Co-authored-by: Kagami Sascha Rosylight <[email protected]>

Author: cscott

README.md

@@ -536,7 +536,7 @@ An operation looks like this:
 The fields are as follows:
 
 * `type`: Always "operation".
-* `special`: One of `"getter"`, `"setter"`, `"deleter"`, `"static"`, `"stringifier"`, or `null`.
+* `special`: One of `"getter"`, `"setter"`, `"deleter"`, `"static"`, `"stringifier"`, or `""`.
 * `idlType`: An [IDL Type](#idl-type) of what the operation returns, if exists.
 * `name`: The name of the operation if exists.
 * `arguments`: An array of [arguments](#arguments) for the operation.
@@ -583,9 +583,7 @@ An attribute member looks like this:
 ```JS
 {
   "type": "attribute",
-  "static": null,
-  "stringifier": null,
-  "inherit": null,
+  "special": "",
   "readonly": false,
   "idlType": {
     "type": "attribute-type",
@@ -605,7 +603,7 @@ The fields are as follows:
 
 * `type`: Always "attribute".
 * `name`: The attribute's name.
-* `special`: One of `"static"`, `"stringifier"`, `"inherit"`, or `null`.
+* `special`: One of `"static"`, `"stringifier"`, `"inherit"`, or `""`.
 * `readonly`: `true` if the attribute is read-only.
 * `idlType`: An [IDL Type](#idl-type) for the attribute.
 * `extAttrs`: An array of [extended attributes](#extended-attributes).