fix: Resolving external references nested inside local references

[Stranger6667]

Fixes #671

[codecov]

Codecov Report

Attention: Patch coverage is 96.42857% with 2 lines in your changes missing coverage. Please review.

Project coverage is 85.48%. Comparing base (29b37f0) to head (1444b41).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/jsonschema/src/keywords/ref_.rs	93.75%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #672      +/-   ##
==========================================
+ Coverage   85.43%   85.48%   +0.04%     
==========================================
  Files          90       90              
  Lines       14038    14072      +34     
==========================================
+ Hits        11994    12029      +35     
+ Misses       2044     2043       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[codspeed-hq]

CodSpeed Performance Report

Merging #672 will degrade performances by 12%

_{Comparing dd/fix-external-in-local (1444b41) with master (29b37f0)}

Summary

❌ 1 (👁 1) regressions
✅ 44 untouched benchmarks

Benchmarks breakdown

	Benchmark	master	dd/fix-external-in-local	Change
👁	try_with_resource[Swagger]	1.7 ms	1.9 ms	-12%