Fix Docker build error by adding Cairo dependencies (#330)

The workshop service Docker build was failing when trying to install
pycairo because the Cairo graphics library was missing from the Alpine
Linux base image.

Changes:
- Added cairo-dev and pkgconfig to build stage dependencies (needed to
  compile pycairo from source)
- Added cairo to runtime stage dependencies (needed for pycairo to run)

This resolves the meson build error: "Dependency 'cairo' not found"

Author: piyushroshan

services/workshop/Dockerfile

@@ -24,7 +24,9 @@ RUN apk add --update --no-cache --virtual .build-deps \
         libffi-dev gcc py3-pip \
         python3-dev \
         musl-dev \
-        libffi-dev
+        libffi-dev \
+        cairo-dev \
+        pkgconfig
 
 ENV PYTHONDONTWRITEBYTECODE=1
 ENV PYTHONUNBUFFERED=1
@@ -36,7 +38,7 @@ RUN pip install wheel && pip wheel . --wheel-dir /app/wheels
 FROM python:3.11-alpine
 COPY --from=build /app /app
 WORKDIR /app
-RUN apk update && apk add --no-cache postgresql-libs curl
+RUN apk update && apk add --no-cache postgresql-libs curl cairo
 RUN pip install --no-index --find-links=/app/wheels -r requirements.txt
 COPY ./certs /app/certs
 COPY health.sh /app/health.sh