feature:add i18n

package.json

src/components/Screenfull/index.vue

src/components/SvgIcon/index.vue

src/icons/svg/international.svg

src/icons/svg/language.svg

src/lang/en.js

src/lang/index.js

src/lang/zh.js

src/main.js

src/router/index.js

src/store/getters.js

src/store/modules/app.js

src/views/i18n/index.vue

src/views/i18n/local.js

src/views/layout/components/Navbar.vue

src/views/layout/components/SidebarItem.vue