Added ffmpeg progress bar via fluent-ffmpeg and progress libs (#57)

* Add fluent-ffmpeg back and cross-platform progress bar

* Repo clean up

Move ts files to src, build and output js files to build folder

* Do not print messages when exit code is 0

this is triggered by signal events

Co-authored-by: kylon <kylonux@gmail.com>

test/test.ts

@@ -1,4 +1,4 @@
-import { parseVideoUrls } from '../utils';
+import { parseVideoUrls } from '../src/utils';
 import puppeteer from 'puppeteer';
 import assert from 'assert';
 import tmp from 'tmp';