feat: reviewpad onboarding (#1904)

* feat: add reviewpad.yml file

* chore: update reviewpad.yml configuration file

* chore: update reviewpad.yml configuration file

* chore: update reviewpad.yml configuration file

* chore: update reviewpad.yml configuration file

* chore: update reviewpad.yml configuration file

* Delete gitstream.cm

* Assign team-reviewer

* Delete gitstream.yml

* Simplify reviewer-assignment logic

---------

Co-authored-by: reviewpad[bot] <104832597+reviewpad[bot]@users.noreply.github.com>
Co-authored-by: Damian Ho <[email protected]>

reviewpad.yml

@@ -0,0 +1,62 @@
+# This file is used to configure Reviewpad.
+# The configuration is a proposal to help you get started.
+# You can use it as a starting point and customize it to your needs.
+# For more details see https://docs.reviewpad.com/guides/syntax.
+
+# Define the list of labels to be used by Reviewpad.
+# For more details see https://docs.reviewpad.com/guides/syntax#label.
+labels:
+  small:
+    description: Pull request is small
+    color: "#76dbbe"
+  medium:
+    description: Pull request is medium
+    color: "#2986cc"
+  large:
+    description: Pull request is large
+    color: "#c90076"
+
+# Define the list of workflows to be run by Reviewpad.
+# A workflow is a list of actions that will be executed based on the defined rules.
+# For more details see https://docs.reviewpad.com/guides/syntax#workflow.
+workflows:
+  # This workflow calls Reviewpad AI agent to summarize the pull request.
+  - name: summarize
+    description: Summarize the pull request
+    run:
+      # Summarize the pull request on pull request synchronization.
+      - if: ($eventType() == "synchronize" || $eventType() == "opened") && $state() == "open"
+        then: $summarize()
+
+  # This workflow assigns a random current developer as a reviewer
+  - name: reviewer-assignment
+    description: Assign a random reviewer to pull requests
+    run:
+      # Automatically assign reviewer when the pull request is ready for review;
+      - if: $isDraft() == false
+        then: $assignReviewer($team("developers-current"), 1, "reviewpad")
+
+  # This workflow labels pull requests based on the total number of lines changed.
+  # This helps pick pull requests based on their size and to incentivize small pull requests.
+  - name: size-labeling
+    description: Label pull request based on the number of lines changed
+    run:
+      - if: $size() < 100
+        then: $addLabel("small")
+        else: $removeLabel("small")
+      - if: $size() >= 100 && $size() < 300
+        then: $addLabel("medium")
+        else: $removeLabel("medium")
+      - if: $size() >= 300
+        then: $addLabel("large")
+        else: $removeLabel("large")
+
+  # This workflow signals pull requests waiting for reviews.
+  # This helps guarantee that pull requests are reviewed and approved by at least one person.
+  - name: check-approvals
+    description: Check that pull requests have the required number of approvals
+    run:
+      # Label pull requests with `waiting-for-review` if there are no approvals;
+      - if: $isDraft() == false && $approvalsCount() < 1
+        then: $addLabel("waiting-for-review")
+