robertmonjo/BigBangTheorem: Lean files for the Big Bang theorem (v1.1.0)

This release contains the Lean supplementary material for the article "If the Big Bang exists, the homogeneous Universe is closed". Contents: BigBangTheorem/BigBangTheorem_Strong.lean: analytic core of the strong version, based on Lipschitz control of the slice-volume function. BigBangTheorem/BigBangTheorem_Weak.lean: analytic core of the weak version, based on finite accumulated expansion. BigBangTheorem/BigBangTheorem_FullFramework.lean: abstract spacetime framework matching the theorem-level hypotheses used in the article. BigBangTheorem/BigBangTheorem_FullStrong.lean: theorem-level formalization of the strong closedness theorem. BigBangTheorem/BigBangTheorem_FullWeak.lean: theorem-level formalization of the weak closedness theorem. Build: lake build