chore: update readme code example to new API.

[saul-jb]

This PR simply fixes the code example provided by the readme.

[mpetrunic]

Please sign CLA agreement

[saul-jb]

Please sign CLA agreement

I don't believe these CLAs are healthy to the opensource ecosystems since they are non-standard and contain legalese that only someone with good understanding of it can fully understand the extent of its meaning. Therefore I will not be signing it, however someone who has the ability to make the changes should update the readme to reflect the new API in a similar fashion to what I have done.

[wemeetagain]

Not sure why we have the CLA here since this is a permissively licensed repo 🤔

[mpetrunic]

Not sure why we have the CLA here since this is a permissively licensed repo 🤔

I think because of that ethereum c++ client that couldn't change license as external contributors were claiming that they only submitted code under previous license so CLA forces everyone to give out any rights to submitted code to chainsafe

[wemeetagain]

Shouldn't that only be an issue when code isn't permissively licensed?

The c++ ethereum client was GPL licensed.

[codecov-commenter]

Codecov Report

Base: 83.29% // Head: 83.26% // Decreases project coverage by -0.03% ⚠️

Coverage data is based on head (91ef484) compared to base (23d49be).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #382      +/-   ##
==========================================
- Coverage   83.29%   83.26%   -0.04%     
==========================================
  Files          48       48              
  Lines       11779    11787       +8     
  Branches     1265     1266       +1     
==========================================
+ Hits         9811     9814       +3     
- Misses       1968     1973       +5     

Impacted Files	Coverage Δ
src/metrics.ts	21.91% <0.00%> (-0.13%)	⬇️
src/tracer.ts	77.45% <0.00%> (-0.06%)	⬇️

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[philknows]

Please sign CLA agreement

I don't believe these CLAs are healthy to the opensource ecosystems since they are non-standard and contain legalese that only someone with good understanding of it can fully understand the extent of its meaning. Therefore I will not be signing it, however someone who has the ability to make the changes should update the readme to reflect the new API in a similar fashion to what I have done.

We've agreed that CLA agreements for Lodestar should not exist on libraries such as this one, but only retained for our main Lodestar monorepo. @q9f is in the process of helping us to remove this requirement and hopefully that will allow this PR to be merged if there's no additional issues.

[q9f]

You can ignore CLA here. It's not meant for the libraries.