feat: migrate webpack file-loader to asset modules

[slorber]

Breaking changes

• require("./img/image.png").default becomes require("./img/image.png")

Motivation

url-loader and file-loader are going to be deprecated in favor of asset modules

This is an attempt to migrate to asset modules.

Some initial problems encountered:

• https://github.com/facebook/docusaurus/commit/2f21d306bdd4d286cc5d25c81adaea2fc77f0474
• https://github.com/webpack/webpack/issues/12900

cc @alexander-akait

Have you read the Contributing Guidelines on pull requests?

yes

Test Plan

preview

Related PRs

Follow-up of https://github.com/facebook/docusaurus/pull/4089

[netlify[bot]]

[V1]

Built with commit 645bf67b5021b76ea5e772f75d21f8bdb2bdb689

https://deploy-preview-4708--docusaurus-1.netlify.app

[slorber]

Note for self, upgrade to css-loader 6 as part of this PR (see also https://github.com/facebook/docusaurus/pull/6424)