refactor: move to 0.2.0

[zeeshanlakhani]

Move us to what will be https://github.com/ucan-wg/invocation/pull/13/files (in review/discussion) vs pre-version.

Includes:

Essentially, all spec things except Effects(fx) and still in-progress Authorization, i.e. ucan-wg/invocation#14.

[codecov]

Codecov Report

Merging #67 (0a137a0) into main (8855e6e) will increase coverage by 13.38%.
The diff coverage is 52.38%.

@@             Coverage Diff             @@
##             main      #67       +/-   ##
===========================================
+ Coverage   26.61%   40.00%   +13.38%     
===========================================
  Files          17       21        +4     
  Lines        1116     1260      +144     
  Branches      305      329       +24     
===========================================
+ Hits          297      504      +207     
+ Misses        700      577      -123     
- Partials      119      179       +60     

Impacted Files	Coverage Δ
homestar/src/lib.rs	100.00% <ø> (ø)
homestar/src/main.rs	0.92% <0.00%> (-0.08%)	⬇️
homestar/src/network/eventloop.rs	0.00% <0.00%> (ø)
homestar/src/workflow/task.rs	42.85% <40.25%> (+42.85%)	⬆️
homestar/src/workflow/nonce.rs	47.36% <47.36%> (ø)
homestar/src/workflow/receipt.rs	52.94% <51.25%> (+16.77%)	⬆️
homestar/src/workflow/prf.rs	53.84% <53.84%> (ø)
homestar/src/workflow/invocation_result.rs	58.33% <58.33%> (ø)
homestar/src/workflow/invocation.rs	59.09% <58.73%> (+59.09%)	⬆️
homestar/src/workflow/pointer.rs	55.55% <62.16%> (+55.55%)	⬆️
... and 9 more