feat: add get_raw_content_cid

[icidasset]

Summary

Adds back the public content CID functionality that was previously removed, under the new name get_raw_content_cid. This method is async as opposed to its predecessor.

Test plan (required)

I've added a new test to wnfs-wasm/tests/public.spec.ts

After Merge

• Does this change invalidate any docs or tutorials? If so ensure the changes needed are either made or recorded
• Does this change require a release to be made? Is so please create and deploy the release

[codecov]

Codecov Report

Merging #385 (89650e9) into main (0964ac4) will increase coverage by 0.05%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #385      +/-   ##
==========================================
+ Coverage   54.80%   54.85%   +0.05%     
==========================================
  Files          57       57              
  Lines        3936     3936              
  Branches      947      947              
==========================================
+ Hits         2157     2159       +2     
+ Misses       1169     1168       -1     
+ Partials      610      609       -1     

Files	Coverage Δ
wnfs/src/public/file.rs	69.82% <ø> (ø)

... and 1 file with indirect coverage changes

[matheus23]

This looks good! Only thing to figure out would be CI, otherwise I approve :)