docs: fix technical typos and file path consistency

[0xkuzeydurden]

Summary

This PR addresses several technical and grammatical typos found in the documentation to improve clarity and ensure technical accuracy.

Changes

• Smart Contract Guide: Corrected the file path for Counter.sol by removing the leading slash (/src/ -> src/) which could cause terminal errors, and standardized the capitalization of TypeScript.
• Mini App Guide: Fixed a grammatical error in the NFT minting instructions (a NFT -> an NFT).

Checklist

• Fits within existing structure
• Consistent terminology
• Uses Mintlify components correctly

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[yasirkonyali170816]

nice