ci: use yarn to package VSCode extension

[danielelisi]

@mweichert reported an error when runnig the VS Code extension packaging pipeline.

https://github.com/ecadlabs/taqueria/runs/4987084269?check_suite_focus=true

Error: Command failed: npm list --production --parseable --depth=99999 --loglevel=error
npm ERR! code ELSPROBLEMS
npm ERR! missing: typescript@^4.5.4, required by taqueria-protocol@npm:@taqueria/[email protected]

vsce is unable to reference a linked dependency and throws an error. There is an open GH Issue for this problem microsoft/vscode-vsce#203

---

Using yarn with vsce seems to solve the issue and the extension gets built successfully. I tested this change in this pipeline which completed successfully https://github.com/ecadlabs/taqueria/runs/4987473254?check_suite_focus=true

[github-actions]

Git Commit	Artifacts
60271b9	Linux MacOS Windows

npm package installation instructions
npm install @taqueria/[email protected]
npm install @taqueria/[email protected]
npm install @taqueria/[email protected]
npm install @taqueria/[email protected]

[cloudflare-workers-and-pages]

Deploying with    Cloudflare Pages

Latest commit:	71a7843
Status:	⚡️  Build in progress...

View logs

[github-actions]

Git Commit	Artifacts
f197759	Linux MacOS Windows

npm package installation instructions
npm install @taqueria/[email protected]
npm install @taqueria/[email protected]
npm install @taqueria/[email protected]
npm install @taqueria/[email protected]