add examples of the two main ways to use the package in README.md

Author: guilhermebodin

README.md

@@ -33,3 +33,97 @@ JobQueueMPI.jl has the following components:
 
 - `Controller`: The controller is responsible for managing the jobs and the workers. It keeps track of the jobs that have been sent and received and sends the jobs to the available workers.
 - `Worker`: The worker is responsible for executing the jobs. It receives the jobs from the controller, executes them, and sends the results back to the controller.
+
+Users can call functions to compute jobs in parallel in two ways:
+ - Building a function and using a `pmap` implementation that will put the function in the job queue and send it to the workers.
+```julia
+using JobQueueMPI
+
+function sum_100(value)
+    return value + 100
+end
+
+sum_100_answer = JobQueueMPI.pmap(sum_100, collect(1:10))
+```
+ - Building the jobs and sending them to workers explicitly. There are examples of this structure in the test folder. This way is much more flexible than the first one, but it requires more code and knowledge about how MPI works.
+
+```julia
+using JobQueueMPI
+
+mutable struct Message
+    value::Int
+    vector_idx::Int
+end
+
+all_jobs_done(controller) = JQM.is_job_queue_empty(controller) && !JQM.any_pending_jobs(controller)
+
+function sum_100(message::Message)
+    message.value += 100
+    return message
+end
+
+function update_data(new_data, message::Message)
+    idx = message.vector_idx
+    value = message.value
+    return new_data[idx] = value
+end
+
+function workers_loop()
+    if JQM.is_worker_process()
+        worker = JQM.Worker()
+        while true
+            job = JQM.receive_job(worker)
+            message = JQM.get_message(job)
+            if message == JQM.TerminationMessage()
+                break
+            end
+            return_message = sum_100(message)
+            JQM.send_job_answer_to_controller(worker, return_message)
+        end
+        exit(0)
+    end
+end
+
+function job_queue(data)
+    JQM.mpi_init()
+    JQM.mpi_barrier()
+
+    T = eltype(data)
+    N = length(data)
+
+    if JQM.is_controller_process()
+        new_data = Array{T}(undef, N)
+
+        controller = JQM.Controller(JQM.num_workers())
+
+        for i in eachindex(data)
+            message = Message(data[i], i)
+            JQM.add_job_to_queue!(controller, message)
+        end
+
+        while !all_jobs_done(controller)
+            if !JQM.is_job_queue_empty(controller)
+                JQM.send_jobs_to_any_available_workers(controller)
+            end
+            if JQM.any_pending_jobs(controller)
+                job_answer = JQM.check_for_job_answers(controller)
+                if !isnothing(job_answer)
+                    message = JQM.get_message(job_answer)
+                    update_data(new_data, message)
+                end
+            end
+        end
+
+        JQM.send_termination_message()
+
+        return new_data
+    end
+    workers_loop()
+    JQM.mpi_barrier()
+    JQM.mpi_finalize()
+    return nothing
+end
+
+data = collect(1:10)
+new_data = job_queue(data)
+```