Add README Package Highlights

[holgerd77]

This PR adds some highlight section for our core packages at the beginning of the README docs.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.89%. Comparing base (934e20d) to head (3666cc2).
Report is 1 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
block	84.33% <ø> (?)
blockchain	89.32% <ø> (ø)
client	?
common	97.51% <ø> (ø)
devp2p	86.78% <ø> (ø)
evm	73.02% <ø> (?)
mpt	89.69% <ø> (-0.06%)	⬇️
statemanager	69.06% <ø> (ø)
static	99.11% <ø> (?)
tx	90.59% <ø> (?)
util	89.36% <ø> (ø)
vm	55.50% <ø> (ø)

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[acolytec3]

Is it important to say mainnet here? That seems to be too narrowly focused since this would work in any chain context that you can specify in our common chain setup, right?

[jochem-brouwer]

One small informational note regarding bundle sizes since those will change with every line of code we merge. LGTM otherwise!

[jochem-brouwer]

Ok, this is fine, but for every PR which we will merge in any of these packages these numbers will likely be incorrect. (Just an informational note. Should we update it for each release to reflect the bundle size?)

[am1r021]

I think we could also consider not including the size here in the docs. There are bundle size tools for this (https://bundlephobia.com/package/@ethereumjs/block@5.3.0)

[holgerd77]

I think it is super important to keep and brings great additional value if we do this (Paul is doing as well). This does not need to be "on point" by KB but gives users strong guidance if they can (bundle size is ok for them, just ballpark number) or cannot (bundle size far too high) use our libraries.

[am1r021]

I think we could also consider not including the size here in the docs. There are bundle size tools for this (https://bundlephobia.com/package/@ethereumjs/block@5.3.0)

[holgerd77]

Sorry, do not have the patience to wait for yet another round of CI and approval, after 2 approvals already done and dismissed, especially for this doc PR. Will admin merge.