N°5621 Move showdown 2.0.0-alpha1 to NPM

Current file header is : /*! showdown v 2.0.0-alpha1 - 25-09-2018 */

Official 2.0.0-alpha doesn't match neither on content nor date :(
Considering date we would be at 1.8.7, but it is also quite different (and has vulnerabilities)
In consequence switching to 2.0.0.

node_modules/is-fullwidth-code-point/index.d.ts

@@ -0,0 +1,17 @@
+/**
+Check if the character represented by a given [Unicode code point](https://en.wikipedia.org/wiki/Code_point) is [fullwidth](https://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms).
+
+@param codePoint - The [code point](https://en.wikipedia.org/wiki/Code_point) of a character.
+
+@example
+```
+import isFullwidthCodePoint from 'is-fullwidth-code-point';
+
+isFullwidthCodePoint('谢'.codePointAt(0));
+//=> true
+
+isFullwidthCodePoint('a'.codePointAt(0));
+//=> false
+```
+*/
+export default function isFullwidthCodePoint(codePoint: number): boolean;