[WebIDE] Set up sourcemaps in Web IDE

MR: chore: Fix web build sourcemap paths (gitlab-vscode-extension!2766 - merged)

Problem to solve

We are fully dependent on console.log and log statements to get insight into the extension running in WebIDE. This is inefficient because we don't have a live-reload of the code.

Goal

Debugging with sourcemaps would mitigate this inefficiency.

Acceptance criteria

• Generate source map files when building Web IDE packages. Ensure that source maps files are included in final bundles and development packages.
• Ensure that source maps of the GitLab Workflow Extension load correctly in the Web IDE.
• (Bonus) Ensure VS Code itself (not the extensions) is published with sourcemaps and you can debug the WebIDE using Developer Tools. VSCode is already published with source maps in the Web IDE.