mathlib3

735b22f8 - feat(analysis/fourier): Riemann-Lebesgue lemma (part 1) (#18361)

feat(analysis/fourier): Riemann-Lebesgue lemma (part 1) (#18361) Add the Riemann-Lebesgue lemma for continuous and compactly-supported functions. Co-authored-by: sgouezel <sebastien.gouezel@univ-rennes1.fr>