Separate all typedefs into their own JSDoc blocks (#878)

Having them in the same block, can be problematic sometimes. For
example when they contain `@template` tags.

lib/index.js

@@ -18,10 +18,14 @@
  *   Parent of `element`.
  * @returns {boolean | null | undefined}
  *   Whether to allow `element` (default: `false`).
- *
+ */
+
+/**
  * @typedef {Partial<JsxRuntimeComponents>} Components
  *   Map tag names to components.
- *
+ */
+
+/**
  * @typedef Deprecation
  *   Deprecation.
  * @property {string} from
@@ -30,7 +34,9 @@
  *   ID in readme.
  * @property {keyof Options} [to]
  *   New field.
- *
+ */
+
+/**
  * @typedef Options
  *   Configuration.
  * @property {AllowElement | null | undefined} [allowElement]
@@ -62,7 +68,9 @@
  *   with `unwrapDisallowed` the element itself is replaced by its children.
  * @property {UrlTransform | null | undefined} [urlTransform]
  *   Change URLs (default: `defaultUrlTransform`)
- *
+ */
+
+/**
  * @callback UrlTransform
  *   Transform all URLs.
  * @param {string} url