feat(amazonq): support Dockerfile files in /dev

Author: michaellandi

packages/amazonq/.changes/next-release/Feature-06d3549d-411e-43e3-a731-d1e435a86577.json

@@ -0,0 +1,4 @@
+{
+	"type": "Feature",
+	"description": "Amazon Q /dev: support `Dockerfile` files"
+}

packages/core/src/shared/filetypes.ts

@@ -347,8 +347,20 @@ export const codefileExtensions = new Set([
     '.zig',
 ])
 
+// Some important files start with a known prefix
+export const codeFilePrefixes = new Set(['Dockerfile'])
+
 /** Returns true if `filename` is a code file. */
 export function isCodeFile(filename: string): boolean {
-    const ext = path.extname(filename).toLowerCase()
-    return codefileExtensions.has(ext)
+    if (codefileExtensions.has(path.extname(filename).toLowerCase())) {
+        return true
+    }
+
+    for (const prefix of codeFilePrefixes) {
+        if (filename.startsWith(prefix)) {
+            return true
+        }
+    }
+
+    return false
 }