Update: modernize dependencies

[BazanAlexandro]

In order to keep the package up to date, following dependencies were updated/changed:

1. removed gulp + bower in favour of webpack (5.51.2) + webpack-dev-server (4.1.0)
2. jquery 2.0.3 -> 3.6.0
3. lodash 1.3.1 -> 4.17.21
4. mustache 0.7.2 -> 4.2.0
5. backbone 1.1.0 -> 1.4.0
6. backbone.marionette 1.2.2 -> 4.1.3
7. qunit -> jest 27.1.0

Some of the packages, especially backbone and backbone.marionette required breaking changes, so tried to update accordingly.

I've really tried to rewrite backbone logic in React, but essentially it's too much work, I guess an lot of logic will be rewritten to React.
Also, removed marionette modules in favour of ES6 ones.

So, let me know what you think

[kevincennis]

Thanks so much for all the work you've put into this.

It's a bit hard to review as-is because the change from 2 spaces to 4 made everything part of the diff. Could you maybe back out those changes for now and submit only the stuff that's actually required to upgrade the dependencies?

[BazanAlexandro]

Thanks so much for all the work you've put into this.

It's a bit hard to review as-is because the change from 2 spaces to 4 made everything part of the diff. Could you maybe back out those changes for now and submit only the stuff that's actually required to upgrade the dependencies?

Uhh, sorry. Will change spacing part. And try to check if it will be a little clearer to understand the diff.