Add static SDK CI workflow (#41)

Add static SDK CI workflow which runs on commits to PRs, merges to main
and daily on main.

---------

Co-authored-by: George Barnett <[email protected]>

Author: rnro

.github/workflows/main.yml

@@ -16,3 +16,7 @@ jobs:
       linux_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
       linux_nightly_next_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
       linux_nightly_main_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -require-explicit-sendable"
+
+  static-sdk:
+    name: Static SDK
+    uses: apple/swift-nio/.github/workflows/static_sdk.yml@main

.github/workflows/pull_request.yml

@@ -32,3 +32,7 @@ jobs:
     with:
       linux_5_9_enabled: false
       linux_5_10_enabled: false
+
+  static-sdk:
+    name: Static SDK
+    uses: apple/swift-nio/.github/workflows/static_sdk.yml@main