docs/bpf: Add table of BPF program types to libbpf docs

Extend the libbpf documentation with a table of program types,
attach points and ELF section names.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20221121121734.98329-1-donald.hunter@gmail.com