feat: add DocsFilter

[forshev]

Description

Added DocsFilter struct. Not in use yet

---

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 31.11111% with 341 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.30%. Comparing base (eec8b16) to head (7a227d0).

Files with missing lines	Patch %	Lines
filtermanager/filter_manager.go	0.00%	215 Missing ⚠️
util/fs.go	30.90%	25 Missing and 13 partials ⚠️
filtermanager/encoding.go	78.80%	17 Missing and 15 partials ⚠️
filtermanager/filter.go	0.00%	16 Missing ⚠️
asyncsearcher/async_searcher.go	22.22%	2 Missing and 5 partials ⚠️
frac/active.go	25.00%	6 Missing ⚠️
frac/active_index.go	0.00%	6 Missing ⚠️
frac/remote.go	0.00%	6 Missing ⚠️
frac/active_lids_map.go	66.66%	5 Missing ⚠️
frac/sealed.go	0.00%	4 Missing ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #371      +/-   ##
==========================================
- Coverage   71.42%   70.30%   -1.12%     
==========================================
  Files         210      214       +4     
  Lines       15637    16055     +418     
==========================================
+ Hits        11168    11288     +120     
- Misses       3664     3954     +290     
- Partials      805      813       +8     

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[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
AggDeep/size=10000-4	ad0347	e19aad
	47818.00 ns/op	54318.00 ns/op	1.14	🔴
AggWide/size=1000-4	ad0347	e19aad
	4780.00 ns/op	5615.00 ns/op	1.17	🔴
And/size=1000-4	ad0347	e19aad
	4.49 ns/op	5.14 ns/op	1.14	🔴

[github-actions]

🔴 Performance Degradation

Some benchmarks have degraded compared to the previous run.
Click on Show table button to see full list of degraded benchmarks.

Show table

Name	Previous	Current	Ratio	Verdict
AggDeep/size=1000-4	ad0347	6ba4f4
	4737.00 ns/op	5455.00 ns/op	1.15	🔴
AggWide/size=1000-4	ad0347	6ba4f4
	4780.00 ns/op	5329.00 ns/op	1.11	🔴
FindSequence_Random/medium-4	ad0347	6ba4f4
	12292.95 MB/s	9431.80 MB/s	0.77	🔴
	86.31 ns/op	108.60 ns/op	1.26	🔴