feat: set up infra, port button Lumo styles to CSS files

[vursen]

Description

• Initialized folder structure for porting the Lumo theme to CSS files
• Ported core Lumo styles to CSS files
• Ported button and icon Lumo styles to CSS files
• Updated the related visual tests to use CSS files
• Added WTR plugins to support running visual tests with both JS-based and CSS-based Lumo versions
  • yarn test:lumo to run with JS-based Lumo
  • yarn test:lumo --ported to run with CSS-based Lumo
  • yarn start --theme=lumo to serve dev pages with JS-based Lumo
  • yarn start --theme=lumo --ported to serve dev pages with CSS-based Lumo
• When using the JS-based version, the plugins automatically remove CSS imports or replace them with the appropriate JS imports
• When using the CSS-based version, the plugins rewrite imports so that Lumo CSS files are applied on top of the new base styles

Part of #9082

Type of change

• Feature

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud