feat(sdk): update README and release 1.0.0

[smartcontracts]

Description
Updates the SDK README and includes a changeset that will trigger the
1.0.0 release of the SDK.

[changeset-bot]

🦋 Changeset detected

Latest commit: 84f63c4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@eth-optimism/sdk	Major
@eth-optimism/message-relayer	Patch
@eth-optimism/replica-healthcheck	Patch

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[netlify]

✔️ Deploy Preview for optimism-sdk ready!

🔨 Explore the source changes: 84f63c4

🔍 Inspect the deploy log: https://app.netlify.com/sites/optimism-sdk/deploys/62267848ed7b760008d5baff

😎 Browse the preview: https://deploy-preview-2278--optimism-sdk.netlify.app/

[codecov-commenter]

Codecov Report

Merging #2278 (84f63c4) into develop (7825c20) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #2278   +/-   ##
========================================
  Coverage    80.08%   80.08%           
========================================
  Files           77       77           
  Lines         2460     2460           
  Branches       450      450           
========================================
  Hits          1970     1970           
  Misses         490      490           

Flag	Coverage Δ
contracts	99.29% <ø> (ø)
core-utils	86.77% <ø> (ø)
data-transport-layer	49.72% <ø> (ø)
sdk	55.75% <ø> (ø)

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