docs: updates docs with new record types

docs/domains-json.md

@@ -21,7 +21,7 @@ In the owner object, the fields `username` and `email` are required. You can how
   "owner": {
     "username": "github-username",
     "email": "any@email"
-  },
+  }
 }
 ```
 
@@ -32,7 +32,7 @@ If you don't wish to share your email address here, please share your twitter or
     "username": "github-username",
     "email": "",
     "twitter": "twitter-handle"
-  },
+  }
 }
 ```
 
@@ -46,14 +46,14 @@ This is a link to your website repository or your github account. This is purely
 
 
 ### record (required)
-This is where you specify how you want to link to your server/webpage.
+This is where you specify the DNS records you wish to use.
 
-Currently, only `CNAME`, `A`, `URL` record types are supported.
+The supported record types are: `CNAME`, `A`, `URL`, `MX` and `TXT`
 
 Here's a few different use cases for the given record types -
 
 * **CNAME**
-CNAME must be a host name (Eg - `something.tld`)
+CNAME must be a host name (Eg - `something.tld`). CNAME cannot be used in conjunction with any other record types.
 ```json
 {
   "record": {
@@ -86,3 +86,25 @@ A record must be a list of ips
 }
 ```
 
+* **MX**
+MX must be a list of host names
+```json
+{
+  "record": {
+    "MX": [
+      "mx1.improvmx.com",
+      "mx2.improvmx.com"
+    ]
+  }
+}
+```
+
+* **TXT**
+TXT can be any string value
+```json
+{
+  "record": {
+    "TXT": "hello world"
+  }
+}
+```