Add block on mentored code review (#1240)

Author: illicitonion

common-content/en/blocks/mentored-code-review/index.md

@@ -0,0 +1,40 @@
++++
+title="Mentored code review"
+
+time = 20
+[objectives]
+    1="Explain what a code reviewer is looking for in a PR."
+    2="Describe elements of the GitHub code review interface."
+    3="List ways someone writing code can make it easier to review."
+[build]
+  render = "never"
+  list = "local"
+  publishResources = false
+
++++
+
+Our learners get feedback on their work through code review.
+At work, colleagues review each others code to understand code, look for problems, and both share and learn better ways of doing things.
+
+At {{<our-name>}} every learner should get code review on their work every week.
+
+{{<note type="activity" title="Live Code Review">}}
+
+Pair up a volunteer with one or more learners. 
+
+- The volunteer will review a pull request, and talk out loud about what they're looking for and doing.
+- The learner(s) will ask questions as they do.
+
+{{</note>}}
+
+<details>
+
+<summary>Hints and tips</summary>
+
+1. How did you understand what the goal of the PR is? Reading the title and description, looking at the coursework exercises, etc.
+2. The uses of the different tabs in a PR: Conversation, Commits, Files changed.
+3. What made a PR easy or hard to review:
+   1. Where unrelated files/lines changed?
+   2. Was code consistently formatted? Did indentation help or hurt understanding?
+4. How did you review the code? Did you read top-to-bottom? Did you jump around into and out-of functions? Did you look at tests? Did you clone the code locally and try running it?
+</details>