Add stats outputs to internal functions

[martinctc]

Summary

This branch adds additional summary stats (e.g. stdev, median, max, min) as an optional output to internal functions, including create_bar_calc() and create_rank_calc()

Changes

The changes made in this PR are:

1. By setting stats = True, the two functions of create_rank_calc() and create_bar_calc() can expose stdev, median, max, and min figures.
2. Version incremented to v0.2.4.
3. Tests modified to accommodate new examples.

Examples

import vivainsights as vi
pq_data = vi.load_pq_data()
vi.create_bar_calc(data = pq_data, metric = 'Collaboration_hours', hrvar = 'Organization', stats = True)

vi.create_rank_calc(
            data=pq_data,
            metric="Emails_sent",
            hrvar=['Organization', 'FunctionType', 'LevelDesignation', 'SupervisorIndicator'],
            mingroup=5,
            stats=True
            )

Checks

• [x] All checks pass (run python -m unittest discover -s tests -f locally)
• [x] Versions are updated in pyproject.toml, setup.py, and docs/conf.py (if applicable)
• [x] NEWS.md has been updated

Notes

This fixes #

<other things, such as how to incorporate new changes>

[martinctc]

Checks have all passed and now v0.2.4 is on PyPI: https://pypi.org/project/vivainsights/0.2.4/