Where should I start if I want to modify/contribute to misago?

Misago is a forum looks nice. And I want to build a forum base on misago.
I want to add some element into frontend of misago. Such as a new captcha service.
But I am new to web development. Even misago have a good coding style and its code is pretty easy to understant. But I don't know where to start editing.

It seems that the source of frontend is bundled into one or two file using webpack(maybe browserify or something else). But I could'nt find any script about bundling. (I knows onlypackage.json, but no scripts there and npm tests failed.).
I tried to use browserify to bundle index.js using browserify index.js misago.js but also failed. Maybe I just missed some setting, but figuring out what I missed is hard for me.

So in a word, could you teach me how should i start if I want to edit the frontend part of misago?

I also tried node .\gulpfile.js

But error still exist:

Microsoft Windows [Version 10.0.17134.345]
(c) 2018 Microsoft Corporation. All rights reserved.

C:\Projects\misago\frontend>node gulpfile.js
C:\Windows\system32\cmd.exe - node  gulpfile.js[31704]: src\node_contextify.cc:628: Assertion `args[1]->IsString()' failed.
 1: 00007FF6446FDC55
 2: 00007FF6446D75C6
 3: 00007FF6446D7691
 4: 00007FF6446AAC9A
 5: 00007FF644ABDD22
 6: 00007FF644ABEF38
 7: 00007FF644ABE26D
 8: 00007FF644ABE18B
 9: 000003F9E33DC6C1

Maybe is it a error of my system?

I'm sorry that it's my fault that not able to run gulpfile.js. After I downgrade node to v8, it works.
Just run gulp build, everything done.

Thanks. I missed the readme.That was a stupid mistake.