add composer alias to turn off xdebug for composer runs

[BinaryKitten]

Description

xdebug is set to be always on within the workspace, this means things like composer run slower when you've not got a listening ide open.

this update adds the composer alias so that xdebug is turned off for duration of composer commands.

Motivation and Context

after booting the workspace and ssh-ing into the workspace environment - ran composer install and due to not having an ide set to listen for connections - was presented with lots of repeated messages about could not connect to debugging client

Xdebug: [Step Debug] Could not connect to debugging client. Tried: host.docker.internal:9000 (through xdebug.client_host/xdebug.client_port).

adding this alias and rebuilding - then running the same composer install

Types of Changes

• New feature (non-breaking change which adds functionality).

Definition of Done Checklist:

• I've read the Contribution Guide.
• I enjoyed my time contributing and making developer's life easier :)