JetFuelBurn: A Python package for calculating fuel burn of commercial aircraft

Improvements Improved the descent logic of utility.ofp.generate_4d_trajectory: the aircraft now holds its altitude until the Top of Descent (TOD) and then descends so as to reach each waypoint's target altitude exactly on arrival, re-evaluating the descent rate as it passes through successive altitude regimes (previously it began descending immediately). Added a regression test for descent from the TOD. Fixed The bundled EUROCONTROL APD sample performance dataset is now included in installed packages. It was previously stored as data.yaml, which the package-data configuration (matching only *.json, *.csv, and *.gz) excluded from the built distribution, so utility.ofp lookups against the shipped dataset failed for installed users. It is now stored as data.json and packaged correctly. Changed Aircraft performance data for utility.ofp is now stored as JSON and read with the standard-library json module instead of YAML, removing the (previously only transitively satisfied) PyYAML dependency. Documentation is now built with Zensical, the successor to Material for MkDocs.