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/yargs/build/lib/utils/process-argv.js

@@ -0,0 +1,17 @@
+function getProcessArgvBinIndex() {
+    if (isBundledElectronApp())
+        return 0;
+    return 1;
+}
+function isBundledElectronApp() {
+    return isElectronApp() && !process.defaultApp;
+}
+function isElectronApp() {
+    return !!process.versions.electron;
+}
+export function hideBin(argv) {
+    return argv.slice(getProcessArgvBinIndex() + 1);
+}
+export function getProcessArgvBin() {
+    return process.argv[getProcessArgvBinIndex()];
+}