Add Netherite sample

[sebastianburckhardt]

This PR adds a sample for a custom DFM backend for the Netherite provider.

So far, the configuration and the instructions are for local operation only.

[scale-tone]

Thanks so much for this, @sebastianburckhardt !
One minor thing: I suggest we do not commit local.settings.json files (keep them .gitignored) and instead provide their entire contents in the README, as it is done here.
Just to reduce chances of accidentally committing credentials.

[scale-tone]

Thanks so much for this, @sebastianburckhardt !
One minor thing: I suggest we do not commit local.settings.json files (keep them .gitignored) and instead provide their entire contents in the README, as it is done here.
Just to reduce chances of accidentally committing credentials.