feat(content): add diverse pages

[Tirokk]

🍰 Pullrequest

Add diverse pages.

Issues

• relates #28
• relates #29
• relates #30
• relates #32
• relates #33
• relates #34
• relates #35
• relates #54

Todo

• [x] about page
• [x] news page
  • [x] add page
  • [x] blog posts: package for VuePress: https://vuepress.vuejs.org/plugin/official/plugin-blog.html
  • [x] move to #52
  • [x] subscribe (newsfeed): package or link to provider?
  • [x] move to #52
• [x] features page
• [x] demos page
• [x] get started page
• [x] learn page
• [x] contribute page
• [x] contact page
• [x] privacy policy page