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

docs/index.rst

@@ -1,5 +1,7 @@
 .. SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
 
+.. _libbpf:
+
 libbpf
 ======
 
@@ -7,6 +9,7 @@ libbpf
    :maxdepth: 1
 
    API Documentation <https://libbpf.readthedocs.io/en/latest/api.html>
+   program_types
    libbpf_naming_convention
    libbpf_build