ExDoc do not build in CI

[ziopio]

We want to be sure documentation can always be built.

Currently rebar3_ex_doc fails silently in CI.

The run is greeen but an error is printed.

 Error: 13:49:12.330 [error] Process #PID<0.139.0> raised an exception
** (MatchError) no match of right hand side value: {:error, {:load_failed, ~c"Failed to load NIF library: 'grisp_rtems.so: cannot open shared object file: No such file or directory'"}}
    /home/runner/work/grisp_connect/grisp_connect/_build/default/lib/grisp/src/grisp_rtems.erl:105: :grisp_rtems.on_load/0
    (kernel 8.5.3) code_server.erl:1317: anonymous fn/1 in :code_server.handle_on_load/5

Warning: 13:49:12.331 [warning] The on_load function for module grisp_rtems returned:
{{:badmatch,
  {:error,
   {:load_failed,
    ~c"Failed to load NIF library: 'grisp_rtems.so: cannot open shared object file: No such file or directory'"}}},
 [
   {:grisp_rtems, :on_load, 0,
    [
      file: ~c"/home/runner/work/grisp_connect/grisp_connect/_build/default/lib/grisp/src/grisp_rtems.erl",
      line: 105
    ]},
   {:code_server, :"-handle_on_load/5-fun-0-", 1,
    [file: ~c"code_server.erl", line: 1317]}
 ]}