Fix examples auto-generation

[TobiasBabin]

What is the motivation?

The "Update generated content" workflow currently fails because required directories are not present.

What does this change do?

The PR simplifies the download of the required input files default.provisioners.yaml for score-compose and zz-default.provisioners.yaml for score-k8s to use wget instead of a git read-tree which obtains the entire directories. That is not required. The change now also creates the target dirs first. This is done in package.json.

Note: The file transform-default-resource-provisioners.js deletes those directories after parsing the input files so the mkdir should not fail on the next run.

As an unrelated issues found during testing, the example page generation currently does not delete previously generated pages. Any source example files that have been removed from the sources will leave those pages behind, causing Hugo build errors because the embedded source files cannot be found anymore. The change to gen-example-pages.js addresses this issue.

What is your testing strategy?

I ran the command npm run gen-all that is executed by the "Update generated content" workflow locally.

Is this related to any issues?

No.

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines

[mathieu-benoit]

LGTM