Update free_subdomain_hosts.txt

[brycampbell]

Papershift.com is a HR system which... "Plan shifts, track working hours, manage vacation days and process payroll – all with one cloud-based software" they offer some subdomain as part of their URLs:

Sample: https://analyzer.sublime.security/?id=01997581-4f04-7d24-b604-c10f56d139d9

Similar Pattern-Based Subdomains Found:
• o1.ptr2897.papershift.com - Uses a pattern with letters and numbers
• status2.papershift.com - Has a number suffix, but the following (as does this, all appear legit)

All Discovered Subdomains: I found 42 total subdomains under papershift.com, including:
• landing.papershift.com
• web.papershift.com
• developers.papershift.com
• app.papershift.com
• api.papershift.com
• cdn.papershift.com
• And many others for staging, testing, and various services

1. url6494.papershift.com appears to be the primary (or only) subdomain following the exact url####.papershift.com pattern
2. I tested ranges around 6494 (6480-6510) and other common ranges but found no additional url#### subdomains
3. The domain resolves but serves a 404 error, suggesting it may be used for tracking, redirects, or inactive content
4. Papershift uses Cloudflare for DNS and hosting infrastructure