add Debian setup instructions for blis build error (#103)

[DhananjayCodes]

What this PR does

Adds a new "Debian Setup Notes" section to README.md
documenting the blis wheel build error and its fix.

Why

While setting up the project on Debian (x86_64) with
Python 3.13, the installation failed when pip attempted
to build blis from source due to missing system-level
compiler dependencies.

Changes

• Added Debian-specific setup instructions to README.md
• Documents the sudo apt install python3-dev build-essential gcc
  fix for the blis build failure

Related Issue

Fixes #103

[Bindkushal]

hey, appreciate the fix, but i think there's a deeper issue here.
i actually hit this same dependency problem while testing on Fedora SoaS and brought it up in the Matrix channel. mentors said SoaS is not a developer environment — kids shouldn't need to run pip install or compile anything to use this activity. ( even pip is not in suagr os you need to install pip first)
the problem with adding sudo apt install python3-dev build-essential gcc to setup docs is that SoaS is a LiveOS — everything wipes on reboot. a kid can't reinstall a full C compiler every session just to run speak-ai. that's not realistic.
from the Matrix discussion, the new SoaS image is supposed to ship with the required wheels and dependencies pre-built. that's probably why there's no official install doc for these — because you shouldn't need to manually install them.
the root cause here is spacy pulling in blis, which needs GCC to compile from source. but espeak-ng already handles phonemization and is a proper system package,
so do we even need Spacy as a hard dependency?
@mebinthattil can you please clarify — should all speak-ai dependencies already be available in the Sugar LiveOS image? are they availble in the latest SOaS release,
and @DhananjayCodes which image version are you testing on? would really help figure out if this is a packaging gap or something else.