[Docs]: Include 'npm install' Step

[Heet Vekariya]

Bug:

• The current documentation for How to Build and Run Odigos Frontend Locally does not include an npm install step, which is essential for setting up the required dependencies. This missing step leads to error.

Change required:

• Add npm install here before npm run build

[Daksh Khurana]

Hey i would like to contribute!
@blumamir Could you please assign it to me :)