docs: add docs (backport #575)

[mergify]

---

This is an automatic backport of pull request #575 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of c76f1a9 has failed:

On branch mergify/bp/release/v1.x.x/pr-575
Your branch is up to date with 'origin/release/v1.x.x'.

You are currently cherry-picking commit c76f1a9.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   docs/0-integrate-the-sdk.md
	new file:   docs/1-overview.md
	new file:   docs/2-how-it-works.md
	new file:   docs/3-searcher-docs.md
	new file:   docs/lanes/1-build-your-own-lane.md
	new file:   docs/lanes/existing-lanes/1-mev.md
	new file:   docs/lanes/existing-lanes/2-free.md

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   tests/e2e/go.mod
	both modified:   tests/e2e/go.sum

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release/v1.x.x@09f12d2). Learn more about missing BASE report.

Additional details and impacted files

@@                Coverage Diff                @@
##             release/v1.x.x     #576   +/-   ##
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  Coverage                  ?   50.53%           
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  Files                     ?       41           
  Lines                     ?     1852           
  Branches                  ?        0           
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  Hits                      ?      936           
  Misses                    ?      823           
  Partials                  ?       93           

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