Creates Frontend Style guide

CONTRIBUTING.md

changelogs/unreleased/28713-fe-style-guide.yml

doc/development/README.md

doc/development/fe_guide/accessibility.md

doc/development/fe_guide/architecture.md

doc/development/fe_guide/design_patterns.md

doc/development/fe_guide/index.md

doc/development/fe_guide/performance.md

doc/development/fe_guide/security.md

doc/development/fe_guide/style_guide_js.md

doc/development/fe_guide/style_guide_scss.md

doc/development/fe_guide/testing.md

doc/development/fe_guide/vue.md

doc/development/frontend.md

doc/development/rake_tasks.md

doc/development/testing.md