docs/bpf: Document BPF_MAP_TYPE_BLOOM_FILTER

Add documentation for BPF_MAP_TYPE_BLOOM_FILTER including kernel
BPF helper usage, userspace usage and examples.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/bpf/20221123141151.54556-1-donald.hunter@gmail.com