Please add example for TLS rootCa verification

[RoSchmi]

First: Thank you very much for your excellent work!
Board: Teensy 4.1
IDE: Platformio
Latest version of NativeEthernet library

I successfully followed the example 'WebClientRepeatingTLS' and could read from the page 'pjrc.com/about/contact.html'.
However I was not successful to get rootCa verification working. Is it supported?
I downloaded the root certificate DST Root CA X3 in the base64 encoded form from pjrc.com.

const char *dst_root_ca =
"-----BEGIN CERTIFICATE-----\n"
"MIIDSjCCAjKgAwIBAgIQRK+wgNajJ7qJMDmGLvhAazANBgkqhkiG9w0BAQUFADA/\n"
"MSQwIgYDVQQKExtEaWdpdGFsIFNpZ25hdHVyZSBUcnVzdCBDby4xFzAVBgNVBAMT\n"
"DkRTVCBSb290IENBIFgzMB4XDTAwMDkzMDIxMTIxOVoXDTIxMDkzMDE0MDExNVow\n"
"PzEkMCIGA1UEChMbRGlnaXRhbCBTaWduYXR1cmUgVHJ1c3QgQ28uMRcwFQYDVQQD\n"
"Ew5EU1QgUm9vdCBDQSBYMzCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEB\n"
"AN+v6ZdQCINXtMxiZfaQguzH0yxrMMpb7NnDfcdAwRgUi+DoM3ZJKuM/IUmTrE4O\n"
"rz5Iy2Xu/NMhD2XSKtkyj4zl93ewEnu1lcCJo6m67XMuegwGMoOifooUMM0RoOEq\n"
"OLl5CjH9UL2AZd+3UWODyOKIYepLYYHsUmu5ouJLGiifSKOeDNoJjj4XLh7dIN9b\n"
"xiqKqy69cK3FCxolkHRyxXtqqzTWMIn/5WgTe1QLyNau7Fqckh49ZLOMxt+/yUFw\n"
"7BZy1SbsOFU5Q9D8/RhcQPGX69Wam40dutolucbY38EVAjqr2m7xPi71XAicPNaD\n"
"aeQQmxkqtilX4+U9m5/wAl0CAwEAAaNCMEAwDwYDVR0TAQH/BAUwAwEB/zAOBgNV\n"
"HQ8BAf8EBAMCAQYwHQYDVR0OBBYEFMSnsaR7LHH62+FLkHX/xBVghYkQMA0GCSqG\n"
"SIb3DQEBBQUAA4IBAQCjGiybFwBcqR7uKGY3Or+Dxz9LwwmglSBd49lZRNI+DT69\n"
"ikugdB/OEIKcdBodfpga3csTS7MgROSR6cz8faXbauX+5v3gTt23ADq1cEmv8uXr\n"
"AvHRAosZy5Q6XkjEGB5YGV8eAlrwDPGxrancWYaLbumR9YbK+rlmM6pZW87ipxZz\n"
"R8srzJmwN0jP41ZL9c8PDHIyh8bwRLtTcm1D9SZImlJnt1ir/md2cXjbDaJWFBM5\n"
"JDGFoqgCWjBH4d1QB7wCCZAA62RjYJsWvIjJEubSfZGL+T0yjWW06XyxV3bqxbYo\n"
"Ob8VZRzI9neWagqNdwvYkQsEjgfbKbYK7p2CNTUQ\n"
"-----END CERTIFICATE-----";

and entered the certificate through:

 client.setCACert((char *)dst_root_ca, strlen(dst_root_ca));

But I got error messages:

Initialize Ethernet with DHCP:
DHCP assigned IP 192.168.1.102
You're connected to the network, IP = 192.168.1.102
TLS ca certificate error.
connecting...
HTTP/1.1 400 Bad Request
Date: Sun, 14 Mar 2021 18:10:08 GMT
Server: Apache/2.4.18 (Ubuntu)
Strict-Transport-Security: max-age=15552000
Cache-Control: stale-while-revalidate=30
Content-Length: 441
Connection: close
Content-Type: text/html; charset=iso-8859-1

<title>400 Bad Request</title>

Bad Request

Your browser sent a request that this server could not understand.
Reason: You're speaking plain HTTP to an SSL-enabled server port.
Instead use the HTTPS scheme to access this URL, please.

---

Apache/2.4.18 (Ubuntu) Server at www.pjrc.com Port 443 SockIndex: 0 SockStatus: 17 RecvErr: -26 SockIndex: 0 SockStatus: 17 RecvErr: -26 ...... ...... ...... Thanks in advance