feat(meta): adding `form` property

docs/usage/elements.md

@@ -37,6 +37,7 @@ export interface MetaElement {
   void: boolean;
   transparent: boolean;
   scriptSupporting: boolean;
+  form: boolean;
 
   /* attributes */
   deprecatedAttributes: string[];
@@ -140,6 +141,11 @@ In HTML5 both the `<script>` and `<template>` tags are considered script-support
 
 [whatwg-scriptsupporting]: https://html.spec.whatwg.org/multipage/dom.html#script-supporting-elements-2
 
+### `form`
+
+Elements which are considered to be a form-element should set this flag to `true`.
+In plain HTML only the `<form>` element is considered a form but when using custom components the form element might be wrapped inside and to make rules related to forms pick up the custom element this flag should be set.
+
 ## Permitted content
 
 ### `attributes`

elements/html5.json

@@ -326,6 +326,7 @@
 
   "form": {
     "flow": true,
+    "form": true,
     "attributes": {
       "autocomplete": ["on", "off"],
       "method": ["get", "post"],

elements/schema.json

@@ -21,6 +21,7 @@
         "transparent": { "type": "boolean" },
         "implicitClosed": { "type": "array", "contains": { "type": "string" } },
         "scriptSupporting": { "type": "boolean" },
+        "form": { "type": "boolean" },
 
         "deprecatedAttributes": {
           "type": "array",

src/dom/htmlelement.spec.ts

@@ -642,6 +642,7 @@ function mockEntry(stub = {}): MetaData {
 			void: false,
 			transparent: false,
 			scriptSupporting: false,
+			form: false,
 		},
 		stub
 	);

src/meta/element.ts

@@ -31,6 +31,7 @@ export interface MetaData {
 	transparent: boolean;
 	implicitClosed?: string[];
 	scriptSupporting: boolean;
+	form: boolean;
 
 	/* attribute */
 	deprecatedAttributes?: string[];

src/meta/table.spec.ts

@@ -322,6 +322,7 @@ function mockEntry(stub = {}): MetaData {
 			void: false,
 			transparent: false,
 			scriptSupporting: false,
+			form: false,
 		},
 		stub
 	);

src/meta/validator.spec.ts

@@ -590,6 +590,7 @@ function mockEntry(stub = {}): MetaData {
 			void: false,
 			transparent: false,
 			scriptSupporting: false,
+			form: false,
 		},
 		stub
 	);