Add codecov config

codecov.yaml

@@ -0,0 +1,24 @@
+codecov:
+  require_ci_to_pass: yes
+  branch: dev-3.x
+
+coverage:
+  precision: 2
+  round: down
+  range: "80...100"
+
+parsers:
+  gcov:
+    branch_detection:
+      conditional: yes
+      loop: yes
+      method: no
+      macro: no
+
+comment:
+  layout: "reach,diff,flags,tree"
+  behavior: default
+  require_changes: no
+  branches:
+    - dev-3.x
+  after_n_builds: 6