Added triggers page to Reference section

This adds a page to describe the various ways an OpenFaaS function can be triggered.
Currently only pointing to various repositories.
This will provide way for users to quickly and easily see the ways
a function can be invoked

Signed-off-by: Burton Rheutan <[email protected]>

Author: burtonr

docs/reference/triggers.md

@@ -0,0 +1,50 @@
+# Triggers
+
+OpenFaaS functions can be triggered easily by any kind of event. A small piece of code will convert from the event-source and trigger the function using the OpenFaaS Gateway API.
+
+The most common use-case is HTTP which acts as a lingua franca between internet-connected systems.
+
+Looking to trigger a function on a schedule? Have a look at the [Cron page](/reference/cron/) for more information
+
+## HTTP
+This is the default, and standard method for interacting with your Functions.
+
+The function URL follows the pattern of:
+```
+https://<gateway URL>:<port>/function/<function name>
+```
+
+> There is also the ability to execute a function asynchronously by replacing `/function/` with `/async-function/` before the function name
+
+## CLI
+Trigger a function using the `faas-cli` by using the function name
+
+```
+echo "triggered" | faas-cli invoke figlet
+```
+
+> CLI invocation can also be async by passing the `-a` flag to the `invoke` call
+
+### Other Event Sources
+
+#### Kafka
+Connect your function(s) to Kafka topics
+
+More information in the Incubator repository: [openfaas-incubator/kafka-connector](https://github.com/openfaas-incubator/kafka-connector)
+
+#### AWS SNS
+Trigger a function from AWS SNS Notifications and Subscriptions
+
+More information in the repository: [affix/OpenFaaS-SNS](https://github.com/affix/OpenFaaS-SNS)
+
+#### CloudEvents
+CloudEvents is a specification for describing event data in a common way. More information on [CloudEvents](https://cloudevents.io/)
+
+Trigger functions from Azure EventGrid with the CloudEvents standard
+
+More information in the repository: [johnmccabe/cloudevents-slack-demo](https://github.com/johnmccabe/cloudevents-slack-demo)
+
+#### RabbitMQ
+Invoke functions from RabbitMQ topics
+
+More information in the repository: [Templum/rabbitmq-connector](https://github.com/Templum/rabbitmq-connector)

mkdocs.yml

@@ -127,6 +127,7 @@ pages:
     - Auth: ./reference/authentication.md
     - CORS: ./reference/cors.md
     - Cron: ./reference/cron.md
+    - Triggers: ./reference/triggers.md
   - Design & Architecture:
     - Gateway: ./architecture/gateway.md
     - Watchdog: ./architecture/watchdog.md