added overwrite / inserts

examples/header.h5

examples/projection_geometry.h5

pyproject.toml

src/h5schemas/header/add_header.py

src/h5schemas/header/overwrite_header.py

src/h5schemas/image/overwrite_image.py

src/h5schemas/projection_geometry/add_projection_geometry.py

...emas/projection_geometry/overwrite_projection_geometry.py