added sendgrid docs

concepts/bindings/README.md

@@ -27,6 +27,7 @@ Every binding has its own unique set of properties. Click the name link to see t
 | [RabbitMQ](../../reference/specs/bindings/rabbitmq.md)   | ✅ | ✅ | Experimental |
 | [Redis](../../reference/specs/bindings/redis.md)         |    | ✅ | Experimental |
 | [Twilio](../../reference/specs/bindings/twilio.md)       |    | ✅ | Experimental |
+| [SendGrid](../../reference/specs/bindings/sendgrid.md)       |    | ✅ | Experimental |
 
 ### Amazon Web Service (AWS)
 

reference/specs/bindings/sendgrid.md

@@ -0,0 +1,41 @@
+# SendGrid Binding Spec
+
+```
+apiVersion: dapr.io/v1alpha1
+kind: Component
+metadata:
+  name: sendgrid
+spec:
+  type: bindings.twilio.sendgrid
+  metadata:
+  - name: emailFrom
+    value: "testapp@dapr.io" # optional 
+  - name: emailTo
+    value: "dave@dapr.io" # optional 
+  - name: subject
+    value: "Hello!" # optional 
+  - name: apiKey
+    value: "YOUR_API_KEY" # required, this is your SendGrid key
+```
+
+- `emailFrom` If set this specifies the 'from' email address of the email message. Optional field, see below.
+- `emailTo` If set this specifies the 'to' email address of the email message. Optional field, see below.
+- `emailCc` If set this specifies the 'cc' email address of the email message. Optional field, see below.
+- `emailBcc` If set this specifies the 'bcc' email address of the email message. Optional field, see below.
+- `subject` If set this specifies the subject of the email message. Optional field, see below.
+- `apiKey` is your SendGrid API key, this should be considered a secret value. Required.
+
+You can specify any of the optional metadata properties on the output binding request too (e.g. `emailFrom`, `emailTo`, `subject`, etc.)
+
+Example request payload
+```
+{
+  "metadata": {
+    "emailTo": "changeme@example.net",
+    "subject": "An email from Dapr SendGrid binding"
+  }, 
+  "data": "<h1>Testing Dapr Bindings</h1>This is a test.<br>Bye!"
+}
+```
+
+> **Note:** In production never place passwords or secrets within Dapr components. For information on securely storing and retrieving secrets refer to [Setup Secret Store](../../../howto/setup-secret-store)