feat: make LocalFileSystem.init public

[alephao]

As mentioned in the discord, I would like to use LocalFileSystem for a implementing something similar to FileMiddleware, but the initializer is currently internal.

LocalFileSystem itself and all of its methods are public.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.54%. Comparing base (e78cde7) to head (9843c9c).
Report is 47 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #451      +/-   ##
==========================================
- Coverage   84.86%   83.54%   -1.33%     
==========================================
  Files          98      103       +5     
  Lines        5320     4303    -1017     
==========================================
- Hits         4515     3595     -920     
+ Misses        805      708      -97     

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