feat: Add support for sv::features attribute. (#446)

[jawoznia]

Remove sv_replies feature as it does not make the change non breaking.

closes #446

[codecov]

Codecov Report

Attention: Patch coverage is 65.62500% with 11 lines in your changes missing coverage. Please review.

Project coverage is 71.95%. Comparing base (d43909d) to head (d3faa82).
Report is 2 commits behind head on feat/replies.

Files with missing lines	Patch %	Lines
sylvia-derive/src/parser/attributes/features.rs	64.70%	6 Missing ⚠️
sylvia-derive/src/entry_points.rs	0.00%	4 Missing ⚠️
sylvia-derive/src/contract/mt.rs	83.33%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           feat/replies     #447      +/-   ##
================================================
- Coverage         72.18%   71.95%   -0.23%     
================================================
  Files                56       59       +3     
  Lines              3577     3634      +57     
================================================
+ Hits               2582     2615      +33     
- Misses              995     1019      +24     

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

[kulikthebird]

I like this approach!