#2386 show custom engine label

[Snapstromegon]

This change adresses the issue in #2386. It changes the output for custom engines as follows:

Before:

[11ty] Writing _site/index2/index.html from ./index2.md (liquid)
[11ty] Writing _site/test/index.html from ./test.md (liquid)
[11ty] Writing _site/description/index.html from ./description.njk
[11ty] Writing _site/cloud/index.html from ./cloud.clowd

After:

[11ty] Writing _site/cloud/index.html from ./cloud.clowd (custom)
[11ty] Writing _site/description/index.html from ./description.njk
[11ty] Writing _site/index2/index.html from ./index2.md (custom/customName)
[11ty] Writing _site/test/index.html from ./test.md (custom/customName)

To configure the "customName", you can now add a key called name to the addExtension options object.

I set this PR to draft for now, to maybe update the naming of the added "name" attribute.

[zachleat]

Sounds good to me! I’d prefer to remove the (custom) and (custom/) part of the content though! e.g.:

[11ty] Writing _site/cloud/index.html from ./cloud.clowd
[11ty] Writing _site/description/index.html from ./description.njk
[11ty] Writing _site/index2/index.html from ./index2.md (customName)
[11ty] Writing _site/test/index.html from ./test.md (customName)

[zachleat]

Shipping with 2.0.0-canary.19, thank you!