fix: correct image name and use relative path for Docker context

[matsest]

Fixes two minor error + an update in the README to get this example up and running:

1. Docker image name should not contain "https://" in the name.

Fixes:

    error: an unhandled error occurred: program exited with non-zero exit code: 1

    error: program failed: waiting for RPCs: https://<reg>.azurecr.io/node-app should not contain a tag: //<reg>.azurecr.io/node-app
    exit status 1

2. Path to Dockerfile context should be relative ("./" vs absolute "/").

Fixes:

  docker:image:Image (node-app):
    error: unable to prepare context: path "/node-app" not found

3. Use a valid region for container apps in Azure. Currently this is limited to canadacentral and northeurope in public environments.

Fixes:

  azure-native:web/v20210301:KubeEnvironment (kubeEnvironment):
    error: Code="LocationNotAvailableForResourceType" Message="The provided location 'westus2' is not available for resource type 'Microsoft.Web/kubeEnvironments'. List of available regions for the resource type is 'northcentralusstage,westcentralus,eastus,westeurope,jioindiawest,northeurope,canadacentral'."

Tested with:

• pulumi v3.22.1
• go version go1.16 linux/amd64
• Docker version 20.10.11, build dea9396

[github-actions]

PR is now waiting for a maintainer to run the acceptance tests.

Note for the maintainer: To run the acceptance tests, please comment /run-example-tests on the PR

[github-actions]

PR is now waiting for a maintainer to run the acceptance tests.

Note for the maintainer: To run the acceptance tests, please comment /run-example-tests on the PR

[mikhailshilkov]

LGTM!