Add description for concrete/parallelChain

Author: henriqueinonhe

EPICS.md

@@ -94,10 +94,9 @@ We need to give a motivation for each exercise, as well as a concrete example of
 - [ ] Concrete - Concurrency Enqueue
 - [ ] Concrete - Concurrency Override
 - [ ] Concrete - Extracting Resolvers
-- [ ] Concrete - Parallel Chain
+- [x] Concrete - Parallel Chain
 - [ ] Concrete - Parallel Chunks
 - [ ] Concrete - Parallel Collect Errors
-- [ ] Concrete - Parallel Collect Errors
 - [ ] Concrete - Parallel Collect Retry
 - [ ] Concrete - Parallel Max Concurrency
 - [x] Concrete - Retry

src/exercises/concrete/parallelChain/README.md

@@ -1,8 +1,20 @@
 # Parallel Chain
 
+**Level: Beginner**
+
+Sometimes we have asynchronous tasks that must be chained off one another, that is, each task depends on the completion of the previous one.
+
+In this exercise we'll explore the idea of dealing with these asynchronous tasks chains, but in a scenario where we have multiple chains and they all must be carried out in parallel.
+
+Each chain has three steps: `firstStep`, `secondStep` and `thirdStep`, where each step uses the data that is returned by the previous step.
+
+You'll be implementing a function that receives a list of strings and from each element of this list, a chain is created.
+
+## Requirements
+
 Implement a function that:
 
 - Signature: `(list: Array<string>) => Promise<Array<string>>`
 - For each element in `list`, calls `firstStep` with it, then calls `secondStep` with the result of the `firstStep` and `thirdStep` with the result of `secondStep`
-- Returns the list of results of `thirdStep`
+- Returns the list of results of `thirdStep` in the order they were called
 - Calls should be made in parallel as much as possible