Add new Client API

Signed-off-by: Helder Correia <174525+helderco@users.noreply.github.com>

tests/plan/client/filesystem/read/fs/relative/test.cue

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"dagger.io/dagger"
+)
+
+dagger.#Plan & {
+	client: filesystem: "../rootfs": read: {
+		contents: dagger.#FS
+		include: ["*.txt"]
+	}
+	actions: test: {
+		[string]: dagger.#ReadFile & {
+			input: client.filesystem."../rootfs".read.contents
+		}
+		valid: {
+			path:     "test.txt"
+			contents: "local directory"
+		}
+		notIncluded: path: "test.log"
+	}
+}