[mod] css files, sidebar.html, to shape sidebar. [add] js on 'topic' class, to implement onclick behavior

[mod] interval between titles & subtitle of English page

See merge request cns-netadmin/cns-hp!44

[mod] sub title in header #9

See merge request cns-netadmin/cns-hp!43

Resolve "Headerの黒帯部分の実装"

See merge request cns-netadmin/cns-hp!42

[fix] lab tiles misaligned & [del] unnecessary lines in index.html & disabled hugo_new_test7.md

See merge request cns-netadmin/cns-hp!41

Resolve "English対応"

Closes #18

See merge request cns-netadmin/cns-hp!40

[fix] sidebar position & disappeared banner problem

See merge request cns-netadmin/cns-hp!39

Merge branch '11-side-bar' of https://www.cns.s.u-tokyo.ac.jp/gitlab/cns-netadmin/cns-hp into 11-side-bar

# Conflicts:
#   themes/cns_hp_theme/layouts/partials/sidebar.html

Resolve "English対応"

See merge request cns-netadmin/cns-hp!38

Resolve "Side barの実装"

Closes #11

See merge request cns-netadmin/cns-hp!37