Add note to bitcoinbinary.org in build info

Actively encourage people to document their build process and provide their work back to the community. Further, push adoption of bitcoinbinary.org as a site for verification and establish sparrow as a well proven/verified wallet.

README.md

@@ -29,6 +29,8 @@ When updating to the latest HEAD
 
 The release binaries are reproducible from v1.5.0 onwards (pre codesigning and installer packaging). More detailed [instructions on reproducing the binaries](docs/reproducible.md) are provided.
 
+> A video documention of your built process uploaded to [bitcoinbinary.org](https://bitcoinbinary.org/) is appreciated. Alternatively check the site if you wish to see if someone else already verified the provided binaries. 
+
 ## Running
 
 If you prefer to run Sparrow directly from source, it can be launched with