Add an Input CRD

We don't currently have any conventions for strongly typed inputs in
Python. I expect that Python functions will just use struct_to_dict to
read their inputs as unstructured data. It's useful to demonstrate
having an input schema in the template, though. Places like
https://marketplace.upbound.io use this CRD schema to document a
function's input.

Signed-off-by: Nic Cope <nicc@rk0n.org>

package/input/template.fn.crossplane.io_inputs.yaml

@@ -0,0 +1,42 @@
+---
+apiVersion: apiextensions.k8s.io/v1
+kind: CustomResourceDefinition
+metadata:
+  name: inputs.template.fn.crossplane.io
+spec:
+  group: template.fn.crossplane.io
+  names:
+    categories:
+    - crossplane
+    kind: Input
+    listKind: InputList
+    plural: inputs
+    singular: input
+  scope: Namespaced
+  versions:
+  - name: v1beta1
+    schema:
+      openAPIV3Schema:
+        description: Input can be used to provide input to this Function.
+        properties:
+          apiVersion:
+            description: 'APIVersion defines the versioned schema of this representation
+              of an object. Servers should convert recognized schemas to the latest
+              internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources'
+            type: string
+          example:
+            description: Example is an example field. Replace it with whatever input
+              you need. :)
+            type: string
+          kind:
+            description: 'Kind is a string value representing the REST resource this
+              object represents. Servers may infer this from the endpoint the client
+              submits requests to. Cannot be updated. In CamelCase. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds'
+            type: string
+          metadata:
+            type: object
+        required:
+        - example
+        type: object
+    served: true
+    storage: true