Autocomplete file name in Markdown

Is it be possible to add filename autocompletion while writing in markdown? I'm trying to create the scope, but it's futile.
In `config.cson` I put:
```
"autocomplete-paths":
scopes: [
{
scopes: [
"source.gfm"
]
prefixes: [
".*\\]\\("
]
extensions: [
"pmd"
]
relative: true
includeCurrentDirectory: true
projectRelativePath: false
}
]
```

Start with the reported `config.cson` autocomplete-paths configuration and reproduce the behavior for the `source.gfm` scope while writing Markdown. Trace how the configured scope, prefix, extension, and relative-path options are matched; the work is done when filename suggestions appear for Markdown links using the intended project-path settings.

Written by the indexing model from the issue text.