feat: drop support for node 12 and jest 24

mentioned in commit c2a55def

mentioned in merge request cypress-html-validate!102 (merged)

mentioned in merge request eslint-config!137 (merged)

mentioned in merge request semantic-release-config!95 (merged)

mentioned in merge request html-validate-vue!135 (merged)

mentioned in merge request html-validate-angular!105 (merged)

mentioned in merge request html-validate-jest-snapshot!84 (merged)

mentioned in merge request demo!107 (merged)

mentioned in merge request html-validate!677 (merged)

mentioned in merge request try-online!107 (merged)

mentioned in merge request stylish!51 (merged)

mentioned in merge request html-validate-vue-webpack-plugin!84 (merged)

mentioned in merge request dgeni-front-matter!66 (merged)

mentioned in merge request example-plugin!63 (merged)