Add nbFile overload for file embedding

[PhilippMDoerner]

This also adds an example.

Note: On my machine locally it was impossible to fully run nimble docs, even after running nimble docsDeps.
Because it doesn't find the happyx custom block:
/home/philipp/dev/nimib/docsrc/interactivity.nim(281, 5) Error: undeclared identifier: 'nbHappyxCode'.

This is caused by the when moduleAvailable(happyx) check failing because
/home/philipp/.nimble/pkgs2/happyx-3.0.0-09a3bb3a93ddca05b973235465eb1f2c6414d5b8/happyx/spa/tag.nim(216, 8) Error: undeclared identifier: 're2'.

I assume that's a happyx problem.

[pietroppeter]

just a minor detail, the rest looks good!

[pietroppeter]

for ref on this, see the discussion we had here, in particular the linked comment: pietroppeter/nimibook#85 (comment)

will wait for preview to build and check

will also look to open an issue about the happy problem for documents

thanks for working on this!

[PhilippMDoerner]

Checks passed!

Regarding the issue, appears I read your comment too late, I already opened HapticX/happyx#170 😅

[Ethosa]

/home/philipp/.nimble/pkgs2/happyx-3.0.0-09a3bb3a93ddca05b973235465eb1f2c6414d5b8/happyx/spa/tag.nim(216, 8) Error: undeclared identifier: 're2'.

@PhilippMDoerner please delete all versions of regex package and install #head version. This should help.

[pietroppeter]

yep, indeed the preview works fine! (if you look at the last check you will see there is a netlify preview and clicking on details let you look at built docs):

regarding happyx, actually happy that you went and opened the issue, I thought it was an issue with nimib.

thanks and have a great day (or likely great night)!

[pietroppeter]

btw, note that LICENSE is bizarrely highlighted (I guess by highlight.js) by mistake...