Fire_occurrence

Fire Load Index (FLI) per the NFDRS (Cohen & Deeming 1985), page 14. FLI combines the Burning Index (BI) with fire occurrence indexes (LOI + MCOI) to provide a comprehensive measure of the expected fire load. Migrated from WildlandFire.jl@126976f2 src/nfdrs.jl:1605 (`FireLoadIndex` @component). Observed-only: BI, LOI, and MCOI are inputs (parameters); FLI is the algebraic output.