Enable bzlmod, update README, fix Swift build

Rather than mess with the WORKSPACE rules, the shortest path to fixing
`blaze build //swift:tests` appeared to be introducing MODULE.bazel.

MODULE.bazel, a.k.a. bzlmod, appears to be the new hotness, so I'll also
try updating the other builds to use it as well.

- https://bazel.build/external/migration
- https://bazel.build/external/overview#workspace-shortcomings
- bazelbuild/bazel#18958

.bazelrc

@@ -1,7 +1,6 @@
 # Options common for all EngFlow remote configurations.
 common --@aspect_rules_ts//ts:skipLibCheck=honor_tsconfig
 common --@aspect_rules_ts//ts:default_to_tsc_transpiler
-common --noenable_bzlmod
 common --noincompatible_check_sharding_support
 
 build:engflow_common --jobs=40

MODULE.bazel

@@ -0,0 +1,15 @@
+"""EngFlow example project"""
+
+module(name = "engflow-example", version = "0.0.0")
+
+bazel_dep(
+    name = "apple_support",
+    version = "1.15.1",
+    repo_name = "build_bazel_apple_support",
+)
+
+bazel_dep(
+    name = "rules_swift",
+    version = "1.18.0",
+    repo_name = "build_bazel_rules_swift"
+)