piaf 0.1.0 requires result
It vendors some libraries that require it:
```
=== ERROR while compiling piaf.0.1.0 =========================================#
context 2.2.0~alpha3 | linux/x86_64 | ocaml-base-compiler.4.14.1 | file:///home/opam/opam-repository
path ~/.opam/4.14/.opam-switch/build/piaf.0.1.0
command ~/.opam/opam-init/hooks/sandbox.sh build dune build -p piaf -j 71
exit-code 1
env-file ~/.opam/log/piaf-7-ccfb59.env
output-file ~/.opam/log/piaf-7-ccfb59.out
File "vendor/dune", line 95, characters 3-9:
95 | result
^^^^^^
Error: Library "result" not found.
-> required by library "piaf.multipart_form" in
_build/default/vendor/multipart_form/lib
-> required by _build/default/META.piaf
-> required by _build/install/default/lib/piaf/META
-> required by _build/default/piaf.install
-> required by alias install
File "vendor/dune", line 60, characters 3-9:
60 | result
^^^^^^
Error: Library "result" not found.
-> required by library "piaf.h2" in _build/default/vendor/ocaml-h2/lib
-> required by _build/default/META.piaf
-> required by _build/install/default/lib/piaf/META
-> required by _build/default/piaf.install
-> required by alias install
File "vendor/dune", line 8, characters 42-48:
8 | (libraries angstrom faraday bigstringaf result)))
^^^^^^
Error: Library "result" not found.
-> required by library "piaf.httpaf" in _build/default/vendor/httpaf/lib
-> required by _build/default/META.piaf
-> required by _build/install/default/lib/piaf/META
-> required by _build/default/piaf.install
-> required by alias install
```
Signed-off-by: Marcello Seri <marcello.seri@gmail.com>