Update dependencies, improve eslint

What does this MR do?

Dependency updates

• Updates dev dependencies
• Fixes peer dependencies (for gitlab-ui and graphql-tag)

Eslint fixes/updates

• Create src/ui/-specific eslint config, which solves various eslint red herrings

CI updates

• remove global before_script in favor of before_script per-job. This fixes sec. jobs failing due to lack-of npm install on their images

Checklist

• Generated new gitlab_figma_plugin_dist.zip (npm run pkg) file if changes have been made to src/
• [-] Added tests for new functionality

Closes #25 (closed)