feat: add user agent to requests to the codecov api

[matt-codecov]

add User-Agent: codecov-uploader/{version} header to outgoing requests to the codecov api so we can track API usage compared to gazebo and codecov-cli or by uploader version

it appears we send a package param to a legacy upload endpoint with this information already which can tell us what proportion of that endpoint's traffic is from this uploader, but setting a user agent across the board tells us for all endpoints, or what proportion of overall API traffic is from this uploader

[thomasrockhu-codecov]

Small nit

[codecov]

Codecov Report

Merging #1250 (8b38a6d) into main (e60489b) will increase coverage by 0.00%.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1250   +/-   ##
=======================================
  Coverage   92.48%   92.48%           
=======================================
  Files          36       36           
  Lines        1357     1358    +1     
  Branches      273      273           
=======================================
+ Hits         1255     1256    +1     
  Misses         70       70           
  Partials       32       32           

Flag	Coverage Δ
aarch64	92.48% <100.00%> (+<0.01%)	⬆️
aarch64-without-git	92.48% <100.00%> (+<0.01%)	⬆️
alpine	92.48% <100.00%> (+<0.01%)	⬆️
alpine-proxy	92.48% <100.00%> (+<0.01%)	⬆️
alpine-without-git	92.48% <100.00%> (+<0.01%)	⬆️
linux	92.48% <100.00%> (+<0.01%)	⬆️
linux-without-git	92.48% <100.00%> (+<0.01%)	⬆️
macos	92.48% <100.00%> (+<0.01%)	⬆️
macos-without-git	92.48% <100.00%> (+<0.01%)	⬆️
windows	92.48% <100.00%> (+<0.01%)	⬆️
windows-without-git	92.48% <100.00%> (+<0.01%)	⬆️

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Files	Coverage Δ
src/helpers/web.ts	85.18% <100.00%> (+0.18%)	⬆️