refactor(v2): import lqip-loader to monorepo, fix build on Node 13, fix lint-staged

[Simek]

Motivation

During discussion with @yangshun about my problems with Node 13 I was able to find that outdated sharp package in one of core dependencies is the root of my issues.

Fortunately it was @endiliey/lqip-loader package which is the fork of original lqip-loader especially created for the Docusaurus anyway. @yangshun asked me if I want to handle the import of this package into Docusaurus monorepo and this PR is the result of that.

It is just a init import, no tests (Endiliey package used old version of mocha), no TS, with the consent of @yangshun.

This PR also fixes:

• V2 build on Node 13 (fixed via sharp bump in docusaurus-plugin-ideal-image and switch to peer dependencies in @docusaurus/lqip-loader) - Enhancement: add support for Node.js 13 lovell/sharp#1909
• lint-staged when adding new files to repo, this was changed in v10 - "⚠ Some of your tasks use git add command." lint-staged/lint-staged#775

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

• I have checked the install, build and run of V2 website locally.
• I have also verified the generated base64 image code after refactor.

Related PRs

• chore(v2): upgrade devDependencies #2538 - lint-staged bump

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[yangshun]

Thank you! Let's make follow up PRs to do:

• Convert tests to Jest
• Potentially convert the loader to TypeScript