perf: 优化首页加载

fix: 修复标签云移动端显示bug

1. 增加标签云功能；2. 优化一些显示

feat: apply #color label to note detail title

Read note.getLabelValue('color') and apply inline style
color on h1.note-title for detail page.

docs: add English README (README.en.md) with language switcher

update: update home card content summary len

fix: fix search bug