[WebIDE] Set up sourcemaps in Web IDE
MR: https://gitlab.com/gitlab-org/gitlab-vscode-extension/-/merge_requests/2766+
## 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
* [x] Generate source map files when building Web IDE packages. Ensure that source maps files are included in final bundles and development packages.
* [x] 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.**
issue