Fix typo in template parsing.

[rhlsthrm]

My function wouldn't build because the webpack config was looking for the wrong key in the parsed YAML.

[michael-menard]

making this change locally give the following error:

`Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.

• configuration.entry should be an non-empty object. -> Multiple entry bundles are created. The key is the chunk name. The value can be a string or an array.`

I think there is a bug maybe in the yaml-cfn dependency?

[ochanje210]

I had the same problem and this fixed it. Thank you!