fix(v2): revert webpack.resolve.symlinks = false

[slorber]

Motivation

Revert change made in #5126 => back to webpack.resolve.symlinks = true

We can't do this change because there's a bug in Webpack 5 cache when resolve.symlinks = false.
Disabling the cache is really painful for the development experience.

More infos reported here:

• Error when using symlinked docs folder: Module parse failed: Assigning to rvalue #3272 (comment)
• Webpack 5 watch mode does not trigger compilation when node_modules file changes webpack/webpack#11612 (comment)

Also adding correct dev watchOptions so that it would work if we decide later to change to resolve.symlinks = false again, or if the user does this with custom Webpack config.

Have you read the Contributing Guidelines on pull requests?

yes

Test Plan

preview

Related PRs

#5126

[netlify]

✔️ [V2]

🔨 Explore the source changes: 772c506

🔍 Inspect the deploy log: https://app.netlify.com/sites/docusaurus-2/deploys/60edd4ca3fb123000730b7f9

😎 Browse the preview: https://deploy-preview-5164--docusaurus-2.netlify.app

[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	82
🟢 Accessibility	98
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

Lighthouse ran on https://deploy-preview-5164--docusaurus-2.netlify.app/

[github-actions]

Size Change: +31 B (0%)

Total Size: 973 kB

Filename	Size	Change
website/build/assets/js/main.********.js	458 kB	+31 B (0%)

ℹ️ View Unchanged

Filename	Size
website/.docusaurus/globalData.json	58.8 kB
website/build/assets/css/styles.********.css	89 kB
website/build/blog/2017/12/14/introducing-docusaurus/index.html	62.3 kB
website/build/blog/index.html	26.3 kB
website/build/docs-tests/index.html	132 kB
website/build/docs-tests/standalone/index.html	19.1 kB
website/build/docs/index.html	46.4 kB
website/build/docs/installation/index.html	53.7 kB
website/build/index.html	27.3 kB

_{compressed-size-action}