Add initial docs/README.md to mime component

[Blacksmoke16]

Context

Add initial docs/README.md to mime component. Not having this was preventing the docs CI job from passing. Updated the component template repo to include this so won't happen again in the future.

Changelog

• Add initial docs/README.md to mime component

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Before merging, remember to add the athena-framework/athena prefix to the PR number in the PR title

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

Flag	Coverage Δ
compiled	8.12% <ø> (ø)
unit	92.78% <ø> (ø)

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Components	Coverage Δ
clock	98.18% <ø> (ø)
console	92.74% <ø> (ø)
dependency_injection	64.28% <ø> (ø)
dotenv	96.80% <ø> (ø)
event_dispatcher	82.75% <ø> (ø)
framework	94.10% <ø> (ø)
image_size	95.03% <ø> (ø)
mercure	93.37% <ø> (ø)
negotiation	97.69% <ø> (ø)
routing	92.96% <ø> (ø)
serializer	87.23% <ø> (ø)
spec	93.54% <ø> (ø)
validator	92.39% <ø> (ø)

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