Minor updates and fixes to functions docs (#385)

Author: jmcx

docs/transformation/functions/index.md

@@ -8,3 +8,17 @@ For low-code style transformations in JSON, refer to [JSON Transformation](../js
     TriggerMesh functions with `tmctl` is a work in progress and not currently supported.
 
     Furthermore, note that TriggerMesh Functions are opinionated and simple. They are aimed to be used for event transformation and do not support external dependencies. Functions that may need external dependencies are best served with something like AWS Lambda or [Knative Functions](https://knative.dev/docs/functions/).
+
+See the [Kubernetes object reference](../../reference/extensions/#extensions.triggermesh.io/v1alpha1.Function) for the Function reference docs.
+
+## Common function configuration options
+
+Below are some parameters you can configure in the function CRD, that apply to all function runtimes. 
+
+| Parameter                 | Description                                                  |
+| ------------------------- | ------------------------------------------------------------ |
+| `adapterOverrides.public` | Boolean. If true, function will be allocated a public URL so that it can be accessed from outside the cluster. Default is false.  |
+| `ceOverrides.extensions`  | Can be used to modify the values of CloudEvents attributes in the event return by the function back to the caller. |
+| `responseIsEvent`  | Boolean. If false, the function will wrap what is returned by the function into the `data` attribute of a CloudEvent and respond back to the caller with it. It will add default CloudEvent metadata attributes, unless values are overriden in `ceOverrides`. If true, expects the user to have returned a complete CloudEvent object, and will no wrap it into the `data` attribute of a new CloudEvent. |
+| `entrypoint`  | Name of the function to be used as an entry point in the code.  |
+| `runtime`  | Currently supported runtime values are `python`, `node`, and `ruby`.  |

docs/transformation/functions/nodejsfunctions.md

@@ -1,5 +1,7 @@
 # NodeJS functions
 
+For information about configuration options across all function runtimes, please head to the [main functions documentation page](index.md).
+
 ## NodeJS empty field transformation example on Kubernetes
 
 ```yaml

docs/transformation/functions/pythonfunctions.md

@@ -25,11 +25,14 @@ metadata:
   name: python-function-hello
 spec:
   runtime: python
-  public: true
+  adapterOverrides:
+    public: true
   entrypoint: endpoint
   code: |
+    import json
     def endpoint(event, context):
-      return "Hello " + event['name']
+      jsonEvent = json.loads(event)
+      return "Hello " + jsonEvent['name']
 ```
 
 You can then create the function with:

docs/transformation/functions/rubyfunctions.md

@@ -1,5 +1,7 @@
 # Ruby functions
 
+For information about configuration options across all function runtimes, please head to the [main functions documentation page](index.md).
+
 ## Ruby date and time event example on Kubernetes
 
 ```YAML