css-loader and more vue-cli consistence

• support assets without protocol, e.g. <img src="//p0.meituan.com/xxx.png" />
• support ~public/path/to/use or ~/public/path/to/use
• support @import '~@/styles/xxx'
• support dynamic injected(prefixed) env, e.g. VUE_APP_ENV=staging yarn vite
• inject process.env.BASE_URL like vue-cli