Add a VSCode devcontainer definition (#916)

Author: GeorgeLyon

.devcontainer/Readme.md

@@ -0,0 +1,13 @@
+## Using VSCode devcontainers
+
+Official tutorial: https://code.visualstudio.com/docs/devcontainers/tutorial
+
+### Recommended Settings for macOS
+
+Some of these are defaults:
+ - Recommended settings for macOS (some of these are defaults):
+    - General:
+      - "Choose file sharing implementation for your containers": VirtioFS (better IO performance)
+    - Resources:
+      - CPUs: Allow docker to use most or all of your CPUs
+      - Memory: Allow docker to use most or all of your memory

.devcontainer/default/Dockerfile

@@ -0,0 +1,10 @@
+FROM swiftlang/swift:nightly-main-jammy
+
+RUN \
+  # Disable apt interactive prompts for this RUN command
+  export DEBIAN_FRONTEND="noninteractive" && \
+  # Update apt package list
+  apt-get update && \
+  # Install sourcekit-lsp dependencies
+  apt-get install -y libsqlite3-dev libncurses5-dev python3
+

.devcontainer/default/devcontainer.json

@@ -0,0 +1,32 @@
+// Reference: https://containers.dev/implementors/json_reference/
+{
+  "name": "SourceKit-LSP",
+  "dockerFile": "Dockerfile",
+
+  // Allow the processes in the container to attach a debugger
+  "capAdd": [ "SYS_PTRACE" ],
+  "securityOpt": [ "seccomp=unconfined" ],
+
+  "mounts": [
+    // Use a named volume for the build products for optimal performance (https://code.visualstudio.com/remote/advancedcontainers/improve-performance#_use-a-targeted-named-volume)
+    "source=${localWorkspaceFolderBasename}-build,target=${containerWorkspaceFolder}/.build,type=volume",
+    // Do the same for experimental background indexing
+    "source=${localWorkspaceFolderBasename}-index-build,target=${containerWorkspaceFolder}/.index-build,type=volume"
+  ],
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "sswg.swift-lang"
+      ],
+      "settings": {
+        "lldb.library": "/usr/lib/liblldb.so",
+        "swift.buildArguments": [
+          "-Xcxx",
+          "-I/usr/lib/swift",
+          "-Xcxx",
+          "-I/usr/lib/swift/Block"
+        ]
+      }
+    }
+  }
+}