Stricter ruff rules

[mrava87]

The following change to pyproject.toml increases the strictness of ruff, at the price of many more errors.

[tool.ruff]
src = ["pyproximal"]
line-length = 88
target-version = "py310"

[tool.ruff.lint]
select = [
  "E",   # pycodestyle errors
  "F",   # pyflakes
  "W",   # pycodestyle warnings
  "B",   # flake8-bugbear
  "EM",  # flake8-errmsg
  "UP",  # pyupgrade
  "I"    # isort
]
ignore = [
  "E203",  # whitespace before ':' (conflicts with Black slicing rules)
  "E501",  # line too long (handled by formatter like Black)
  "E402",   # module level import not at top of file (scripts / Sphinx config)
  "UP031" # use of old '%' formatting instead of f-strings
]

These seem to be all easy fixable though. This change and related fixes should be done in a dedicated PR after #241 is merged