Add bors

Author: eldruin

.github/bors.toml

@@ -0,0 +1,11 @@
+block_labels = ["needs-decision"]
+delete_merged_branches = true
+required_approvals = 1
+status = [
+  "ci-linux (stable, x86_64-unknown-linux-gnu)",
+  "ci-linux (stable, x86_64-unknown-linux-musl)",
+  "ci-linux (beta, x86_64-unknown-linux-gnu)",
+  "ci-linux (beta, x86_64-unknown-linux-musl)",
+  "ci-linux (1.31.0, x86_64-unknown-linux-gnu)",
+  "ci-linux (1.31.0, x86_64-unknown-linux-musl)",
+]