chore(github): integrate bors

.github/bors.toml

@@ -0,0 +1,13 @@
+status = [
+    "Check",
+    "Lints",
+    "Formatting",
+    "Test suite",
+    "Audit check",
+    "Links",
+    "Check Rust version",
+]
+delete_merged_branches = true
+update_base_for_deletes = true
+cut_body_after = "<details>"
+commit_title = "chore(pull): merge ${PR_REFS}"

.github/workflows/ci.yml

@@ -1,12 +1,12 @@
 name: Continuous Integration
 
 on:
+  pull_request:
   push:
     branches:
       - main
-  pull_request:
-    branches:
-      - main
+      - staging # for bors
+      - trying # for bors
   schedule:
     - cron: "0 0 * * 0"