feat: add skeleton of pressure loss nub

src/compute-node.ts

src/index.ts

src/pipe_flow/pl_lechaptcalmon.ts

src/pipe_flow/pl_lechaptcalmon_params.ts

src/pipe_flow/pressureloss.ts

src/pipe_flow/pressureloss_law.ts

src/pipe_flow/pressureloss_params.ts