Add support for DNS over TLS and DNS over HTTPS

[onedr0p]

Describe the feature request

It would be great if gatus could support DoH and DoT when using the DNS endpoint...

endpoints:
  - name: example-dns-query
    url: "8.8.8.8"                     # Address of the DNS server to use
    # url: "tcp-tls:1.1.1.1:853"       # Address of the DNS server to use (DoT)
    # url: "https://1.1.1.1/dns-query" # Address of the DNS server to use (DoH)
    dns:
      query-name: "example.com"
      query-type: "A"
    conditions:
      - "[BODY] == 93.184.215.14"
      - "[DNS_RCODE] == NOERROR"

Why do you personally want this feature to be implemented?

In some environments port 53 is nat'ed to an internal DNS server, using DoT or DoH can circumvent this.

How long have you been using this project?

18 months+

Additional information

No response

[onedr0p]

It would also be great to support this in the connectivity.checker.target field:

connectivity:
  checker:
    target: tcp-tls:1.1.1.1:853
    interval: 1m