Add ConnectHealthMD White Label Template (#737)

# Description

Adding a new template for the ConnectHealthMD white-label service. This
allows professionals to connect their subdomains (e.g. www) to our SaaS
edge.

## Type of change

- [x] New template
- [ ] Bug fix (non-breaking change which fixes an issue in the template)
- [ ] New feature (non-breaking change which adds functionality to the
template)
- [ ] Breaking change (fix or feature that would cause existing template
behavior to be not backward compatible)

# How Has This Been Tested?

- [x] Schema validated using JSON Schema
[template.schema](./template.schema)
- [ ] Template functionality checked using [Online
Editor](https://domainconnect.paulonet.eu/dc/free/templateedit)
- [ ] Template is checked using [template
linter](https://github.com/Domain-Connect/dc-template-linter)
- [x] Template file name follows the pattern
`<providerId>.<serviceId>.json`
- [x] resource URL provided with `logoUrl` is actually served by a
webserver

# Checklist of common problems

- [ ] digital signatures are used and `syncPubKeyDomain` specified
  - *Comment: Public template, syncBlock is false.*
- [ ] `syncRedirectDomain` is specified when intended to use
`redirect_uri` parameter in the synchronous flow
- [x] no TXT record with SPF content (i.e. `"v=spf1 ..."`) instead of
using SPFM record type on APEX
- [x] `txtConflictMatchingMode` is set on TXT records which shall be
unique on a label (like DMARC)
- [x] variables are set to the smallest scope needed
- [x] no variables as a host name to apply template on subdomain instead
of standard `host` parameter
- [x] no explicit usage of `%host%` variable in `host` attribute
- [x] `essential` setting is used on records, which the user shall be
able to change or remove manually later without dropping the whole
template

# Example variable values

verifyToken: a1b2c3d4e5f6

Author: connecthealthmd

connecthealthmd.com.white-label.json

@@ -0,0 +1,27 @@
+{
+    "providerId": "connecthealthmd.com",
+    "providerName": "ConnectHealthMD",
+    "syncPubKeyDomain": "connecthealthmd.com",    
+    "serviceId": "white-label",
+    "serviceName": "ConnectHealthMD White Label",
+    "version": 1,
+    "logoUrl": "https://www.connecthealthmd.com/assets/images/ch_logo.png",
+    "description": "Connect your domain to your ConnectHealthMD professional storefront.",
+    "variableDescription": "The subdomain you want to connect (usually 'www')",
+    "syncBlock": false,
+    "hostRequired": true,
+    "records": [
+        {
+            "type": "CNAME",
+            "host": "@",
+            "pointsTo": "edge.connecthealthmd.com",
+            "ttl": 3600
+        },
+        {
+            "type": "TXT",
+            "host": "_ch-verify",
+            "data": "%verifyToken%",
+            "ttl": 3600
+        }
+    ]
+}