This is the web site of Denis Defreyne, a software engineer living in Berlin.
There are multiple ways of associating metadata in plaintext files, depending on the file format:
The Front matter (used in Nanoc, Jekyll, …) can be used for any plaintext file format.
AsciiDoc has its own metadata format.
Nanoc only supports front matter natively, though with some preprocessor logic, other types of metadata could be extracted.