05/01: add explanation draft

Author: kettanaito

exercises/05.performance/01.solution.profiling-slow-tests/README.mdx

@@ -12,3 +12,11 @@ Duration  2.19s (transform 16ms, setup 0ms, collect 10ms, tests 2.00s, environme
 ```
 
 This is a good overlook at which areas of your test take how much time. Understanding what each area does sets up your map for future debugging.
+
+## Step 2. Use the profiler
+
+```sh
+npm i vitest-profiler --save-dev
+```
+
+## Step 3. Analyze the generated CPU/heap profiles