Housekeeping (#8)

* Rename the provider to dockerbuild.
* Add Makefile targets required by CI.
* Add per-language test targets compatible with CI.
* Fix broken example yaml.
* Add gitignore exclusions to fix SDK generation in CI.
* Fix lint errors.
* Vendor pulumi CLI via `tools.go` instead of `.pulumi`.
* Consolidate `go.mod`s into one file, with a minimal `go.mod` for the
Go SDK.
* Add codecov.

.github/dependabot.yml

@@ -0,0 +1,15 @@
+version: 2
+updates:
+  - package-ecosystem: gomod
+    directory: /
+    schedule:
+      interval: daily
+    groups:
+      pulumi:
+        patterns:
+          - "github.com/pulumi/*"
+        exclude-patterns:
+          - "k8s.io/utils"
+    labels:
+      - dependencies
+      - impact/no-changelog-required