fix: add missing pkg-config package (#30)

Build fails in nightly with the following error:

	#27 4.029   × Getting requirements to build wheel did not run
	    successfully.
	#27 4.029   │ exit code: 1
	#27 4.029   ╰─> [24 lines of output]
	#27 4.029       /bin/sh: 1: pkg-config: not found
	#27 4.029       /bin/sh: 1: pkg-config: not found
	#27 4.029       Trying pkg-config --exists mysqlclient
	#27 4.029       Command 'pkg-config --exists mysqlclient' returned
	    non-zero exit status 127.
	#27 4.029       Trying pkg-config --exists mariadb
	#27 4.029       Command 'pkg-config --exists mariadb' returned non-zero
	    exit status 127.
	#27 4.029       Traceback (most recent call last):
	#27 4.029         File
	    "/app/venv/lib/python3.8/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py",
	line 353, in <module>
	#27 4.029           main()
	#27 4.029         File
	    "/app/venv/lib/python3.8/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py",
	line 335, in main
	#27 4.029           json_out['return_val'] =
	    hook(**hook_input['kwargs'])
	#27 4.029         File
	    "/app/venv/lib/python3.8/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py",
	line 118, in get_requires_for_build_wheel
	#27 4.029           return hook(config_settings)
	#27 4.029         File
	    "/tmp/pip-build-env-td0z_pds/overlay/lib/python3.8/site-packages/setuptools/build_meta.py",
	line 355, in get_requires_for_build_wheel
	#27 4.029           return self._get_build_requires(config_settings,
	    requirements=['wheel'])
	#27 4.029         File
	    "/tmp/pip-build-env-td0z_pds/overlay/lib/python3.8/site-packages/setuptools/build_meta.py",
	line 325, in _get_build_requires
	#27 4.029           self.run_setup()
	#27 4.029         File
	    "/tmp/pip-build-env-td0z_pds/overlay/lib/python3.8/site-packages/setuptools/build_meta.py",
	line 341, in run_setup
	#27 4.029           exec(code, locals())
	#27 4.029         File "<string>", line 154, in <module>
	#27 4.029         File "<string>", line 48, in get_config_posix
	#27 4.029         File "<string>", line 27, in find_package_name
	#27 4.029       Exception: Can not find valid pkg-config name.
	#27 4.029       Specify MYSQLCLIENT_CFLAGS and MYSQLCLIENT_LDFLAGS env
	    vars manually

tutornotes/templates/notes/build/notes/Dockerfile

@@ -1,12 +1,19 @@
 {% if is_buildkit_enabled() %}# syntax=docker/dockerfile:1.4{% endif %}
 FROM docker.io/ubuntu:20.04
 
+ENV DEBIAN_FRONTEND=noninteractive
 RUN {% if is_buildkit_enabled() %}--mount=type=cache,target=/var/cache/apt,sharing=locked \
   --mount=type=cache,target=/var/lib/apt,sharing=locked{% endif %} \
   apt update && \
   apt upgrade -y && \
-  # python 3.8
-  apt install -y language-pack-en git python3 python3-pip python3-venv libmysqlclient-dev
+  apt install -y \
+    language-pack-en \
+    git \
+    python3 \
+    python3-pip \
+    python3-venv \
+    libmysqlclient-dev \
+    pkg-config
 RUN ln -s /usr/bin/python3 /usr/bin/python
 
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