refactor: update svgprep plugin for webpack 5

[damianstasik]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

This PR updates the SVG Prep plugin for webpack 5 as the current version throws the following warning:

(node:95614) [DEP_WEBPACK_COMPILATION_ASSETS] DeprecationWarning: Compilation.assets will be frozen in future, all modifications are deprecated.
BREAKING CHANGE: No more changes should happen to Compilation.assets after sealing the Compilation.
	Do changes to assets earlier, e. g. in Compilation.hooks.processAssets.
	Make sure to select an appropriate stage from Compilation.PROCESS_ASSETS_STAGE_*.

Related issue: #1859

Approach

1. The plugin now uses the recommended processAssets hook instead of emit.
2. Replaced tapAsync with tapPromise to simplify the code with async/await.
3. There is now an additional hook that wraps the previous one, it is required to have access to the current compilation process.
4. Replaced !!name.match(/\.svg$/) with name.endsWith('.svg') to make it easier to understand how the array is filtered.
5. Used compilation.emitAsset instead of just putting new objects into compilation.assets which was the old way (pre-webpack 5) of emitting new assets.
6. The emitted source is now wrapped with RawSource to let webpack-sources handle the final format (which usually is an object with source and size properties).

TODOs before merging

• A changelog entry is created automatically using the pull request title (do not manually add a changelog entry)

[parse-github-assistant]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[mtrezza]

It builds fine, please again let me know when this is ready for review.

[damianstasik]

@mtrezza It is ready 👍

[mtrezza]

Looks good! Another annoying deprecation message less is candy for the eye!

[parseplatformorg]

🎉 This pull request has been released in version 3.3.0-alpha.5

[parseplatformorg]

🎉 This change has been released in version 3.3.0-beta.1

[parseplatformorg]

🎉 This change has been released in version 3.3.0