Modifies buildkit task according to the new reorg proposal

Changes include:
   - adds version label
   - adds a minimum pipeline versions supported by the task
   - adds tags for task
   - modified description to add a summary

This patch moves the buildkit files to the task directory and
renames the yaml file
   - The yaml filename is changed to match the resource name.

Issue: #386

Signed-off-by: Shivam Mukhade <smukhade@redhat.com>

task/buildkit/0.1/buildkit.yaml

@@ -2,7 +2,15 @@ apiVersion: tekton.dev/v1beta1
 kind: Task
 metadata:
   name: buildkit
+  labels:
+    app.kubernetes.io/version: "0.1"
+  annotations:
+    tekton.dev/pipelines.minVersion: "0.12.1"
+    tekton.dev/tags: image-build
 spec:
+  description: >-
+    This Task builds source into a container image using Moby BuildKit.
+
   params:
   - name: DOCKERFILE
     description: The name of the Dockerfile