Add pre-commit checks to the core examples

.pre-commit-config.yaml

examples/core_examples/15d_gaussian.py

...ples/alternative_samplers/linear_regression_bilby_mcmc.py

..._examples/alternative_samplers/linear_regression_pymc3.py

...ive_samplers/linear_regression_pymc3_custom_likelihood.py

examples/core_examples/conditional_prior.py

examples/core_examples/dirichlet.py

examples/core_examples/gaussian_example.py

examples/core_examples/grid_example.py

examples/core_examples/hyper_parameter_example.py

examples/core_examples/linear_regression.py

examples/core_examples/linear_regression_grid.py

examples/core_examples/linear_regression_unknown_noise.py

examples/core_examples/logo/sample_logo.py

examples/core_examples/multivariate_gaussian_prior.py

examples/core_examples/occam_factor_example.py

examples/core_examples/radioactive_decay.py

examples/core_examples/slabspike_example.py