fix: Add gfortran to Ubuntu install

[chadac]

Currently Ubuntu install when contributing fails due to a missing Fortran compiler. Suggest adding gfortran as a default.

Steps to reproduce:

docker run -it --rm -v $PWD:/app ubuntu:latest
apt-get install python3 python3-pip python3-venv build-essential
python3 -m venv /.venv
source /.venv/bin/activate
pip install poetry
cd /app
poetry install

[codecov]

Codecov Report

Merging #92 (6814e71) into master (b0ed09d) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #92   +/-   ##
======================================
  Coverage    0.24%   0.24%           
======================================
  Files          10      10           
  Lines        2047    2047           
  Branches      487     487           
======================================
  Hits            5       5           
  Misses       2042    2042           

Flag	Coverage Δ
unittests	0.24% <ø> (ø)

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[amirhessam88]

LGTM