Not serving .dotfiles and .dotfolders

[douxxtech]

This PR makes NASMServer return a 403 when the client tries to fetch a .dotfile or a ./dotfolder, by default. A SERVE_DOTS config key has been added and can be set to true. Anything other will make it fallback to false.

For security and performance reasons, the 403 will be returned even if the asked dot does not exist

[github-actions]

threads: 4 (auto), conns: 50, duration: 20s

[wrk]
Running 20s test @ http://127.0.0.1:8080/
  4 threads and 50 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     4.59ms    7.47ms 212.75ms   99.64%
    Req/Sec     1.76k   378.95     2.80k    72.38%
  140273 requests in 20.04s, 214.71MB read
  Socket errors: connect 0, read 99, write 0, timeout 0
Requests/sec:   7000.56
Transfer/sec:     10.72MB