Fix frontend readme

[mihaidusmanu]

Description

README of frontend seems to be outdated (wrong folder structure) leading to:

FAILURE: Build failed with an exception.

* What went wrong:
The specified project directory '/home/mihaidusmanu/sources/serve/frontend/frontend' does not exist.

This change fixes that.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Feature/Issue validation/testing

The command in the README now successfully runs.

Checklist:

• Did you have fun?
• N/A - Have you added tests that prove your fix is effective or that this feature works?
• N/A - Has code been commented, particularly in hard-to-understand areas?
• N/A - Have you made corresponding changes to the documentation?