chore: temporary shutdown

[hi-ogawa]

For now, we made a redirection:

$ curl -X GET -I https://ytsub-v3-hiro18181.vercel.app/
HTTP/2 307 
cache-control: public, max-age=0, must-revalidate
content-type: text/plain
date: Thu, 04 Apr 2024 08:04:45 GMT
location: https://github.com/hi-ogawa/ytsub-v3
server: Vercel
strict-transport-security: max-age=63072000; includeSubDomains; preload
x-vercel-id: hnd1::z2g2s-1712217885102-90b74f13013f