dagger input bool implementation

Signed-off-by: Guillaume de Rouville <guillaume.derouville@gmail.com>

tests/cli/input/bool/main.cue

@@ -0,0 +1,11 @@
+package testing
+
+import (
+	"alpha.dagger.io/dagger"
+)
+
+first: dagger.#Input & {bool | *false}
+
+if first == true {
+	second: true
+}