[ENH]: Add support for multiple preprocessors in the pipeline

[synchon]

• description of feature/fix
• tests added/passed
• add an entry for the latest changes

This PR refactors the pipeline internals to add support for multiple preprocessors.

[github-actions]

PR Preview Action v1.4.4
Preview removed because the pull request was closed.
2023-10-18 13:18 UTC

[codecov]

Codecov Report

Merging #263 (f80d532) into main (9689b02) will decrease coverage by 0.04%.
The diff coverage is 90.47%.

@@            Coverage Diff             @@
##             main     #263      +/-   ##
==========================================
- Coverage   92.38%   92.35%   -0.04%     
==========================================
  Files          86       86              
  Lines        3837     3846       +9     
  Branches      748      753       +5     
==========================================
+ Hits         3545     3552       +7     
- Misses        187      188       +1     
- Partials      105      106       +1     

Flag	Coverage Δ
docs	100.00% <ø> (ø)
junifer	92.35% <90.47%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
junifer/api/functions.py	96.35% <100.00%> (+0.07%)	⬆️
junifer/markers/collection.py	100.00% <100.00%> (ø)
junifer/api/cli.py	70.19% <33.33%> (-1.38%)	⬇️