fix(meta): make all meta properties optional in type declaration

In practice all where optional but the type never reflected this.

docs/usage/elements.md

@@ -23,33 +23,33 @@ Each entry can contain the following properties:
 ```typescript
 export interface MetaElement {
   /* content categories */
-  metadata: boolean | PropertyExpression;
-  flow: boolean | PropertyExpression;
-  sectioning: boolean | PropertyExpression;
-  heading: boolean | PropertyExpression;
-  phrasing: boolean | PropertyExpression;
-  embedded: boolean | PropertyExpression;
-  interactive: boolean | PropertyExpression;
+  metadata?: boolean | PropertyExpression;
+  flow?: boolean | PropertyExpression;
+  sectioning?: boolean | PropertyExpression;
+  heading?: boolean | PropertyExpression;
+  phrasing?: boolean | PropertyExpression;
+  embedded?: boolean | PropertyExpression;
+  interactive?: boolean | PropertyExpression;
 
   /* element properties */
-  deprecated: boolean | string | DeprecatedElement;
-  foreign: boolean;
-  void: boolean;
-  transparent: boolean;
-  scriptSupporting: boolean;
-  form: boolean;
+  deprecated?: boolean | string | DeprecatedElement;
+  foreign?: boolean;
+  void?: boolean;
+  transparent?: boolean;
+  scriptSupporting?: boolean;
+  form?: boolean;
 
   /* attributes */
-  deprecatedAttributes: string[];
-  requiredAttributes: string[];
-  attributes: PermittedAttribute;
+  deprecatedAttributes?: string[];
+  requiredAttributes?: string[];
+  attributes?: PermittedAttribute;
 
   /* permitted data */
-  permittedContent: Permitted;
-  permittedDescendants: Permitted;
-  permittedOrder: PermittedOrder;
-  requiredAncestors: string[];
-  requiredContent: string[];
+  permittedContent?: Permitted;
+  permittedDescendants?: Permitted;
+  permittedOrder?: PermittedOrder;
+  requiredAncestors?: string[];
+  requiredContent?: string[];
 
   /* inheritance */
   inherit?: string;

src/meta/element.ts

@@ -25,22 +25,22 @@ export interface MetaData {
 	inherit?: string;
 
 	/* content categories */
-	metadata: boolean | PropertyExpression;
-	flow: boolean | PropertyExpression;
-	sectioning: boolean | PropertyExpression;
-	heading: boolean | PropertyExpression;
-	phrasing: boolean | PropertyExpression;
-	embedded: boolean | PropertyExpression;
-	interactive: boolean | PropertyExpression;
+	metadata?: boolean | PropertyExpression;
+	flow?: boolean | PropertyExpression;
+	sectioning?: boolean | PropertyExpression;
+	heading?: boolean | PropertyExpression;
+	phrasing?: boolean | PropertyExpression;
+	embedded?: boolean | PropertyExpression;
+	interactive?: boolean | PropertyExpression;
 
 	/* element properties */
-	deprecated: boolean | string | DeprecatedElement;
-	foreign: boolean;
-	void: boolean;
-	transparent: boolean;
+	deprecated?: boolean | string | DeprecatedElement;
+	foreign?: boolean;
+	void?: boolean;
+	transparent?: boolean;
 	implicitClosed?: string[];
-	scriptSupporting: boolean;
-	form: boolean;
+	scriptSupporting?: boolean;
+	form?: boolean;
 
 	/* attribute */
 	deprecatedAttributes?: string[];