fix: custom-inject-decorator.ts direct link to md

[sandeep17sf]

convert direct link of example custom-inject-decorator.ts to MD version

Checklist

• [ ] DCO (Developer Certificate of Origin) signed in all commits
• [ ] npm test passes on your machine
• [ ] New tests added or existing tests modified to cover all changes
• [ ] Code conforms with the style guide
• [ ] API Documentation in code was updated
• [x] Documentation in /docs/site was updated
• [ ] Affected artifact templates in packages/cli were updated
• [ ] Affected example projects in examples/* were updated

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[raymondfeng]

@sandeep17sf Please sign off the commit.

[dhmlau]

@sandeep17sf, could you please sign off the commit? Here is the reference: https://loopback.io/doc/en/contrib/code-contrib.html#signing-off-commits-using-dco. Thanks.

[dhmlau]

closing as abandoned.