Update the featured image factory to specify the file causing an exception

[caendesilva]

We throw an exception when an image without a source is specified, but we don't mention which file. Now we do.

// Old
No featured image source was found
// New
No featured image source was found in "_posts/my-new-post.md"

[codecov]

Codecov Report

Merging #1409 (689db9c) into master (d5b24d8) will not change coverage.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##             master    #1409     +/-   ##
===========================================
  Coverage     99.97%   99.97%             
- Complexity     1705     3410   +1705     
===========================================
  Files           180      360    +180     
  Lines          4619     9240   +4621     
===========================================
+ Hits           4618     9238   +4620     
- Misses            1        2      +1     

Files	Coverage Δ
...rk/src/Framework/Factories/BlogPostDataFactory.php	100.00% <100.00%> (ø)
...k/src/Framework/Factories/FeaturedImageFactory.php	100.00% <100.00%> (ø)

... and 180 files with indirect coverage changes