relative links in file system documents are not resolved correctly

[Georgi Pavlov]

What happened:
A markdown in a document at //a.md for a relative link like [test](./b.md) that is not in download scope gets resolved to [test](/<path>/a.md/b.md)

What you expected to happen:
The resolved path should be /<path>/b.md instead

How to reproduce it (as minimally and precisely as possible):

1. Create file a.md with content:

   [test](./a.md)
   

2. Create manifest like:

   structure:
      - source: <path>/a.md
   

   where <path> is path to the a.md file you created.
3. Invoke docforge with that manifest and inspect the results in a.md
   You should observe

   [test](/<path>/a.md/a.md)
   

   where <path> is path to the a.md file you created.