docs: ♻️ merge API Reference and Universe menu entries

Signed-off-by: jffarge <jf@dagger.io>

docs/reference/io.md

@@ -0,0 +1,71 @@
+---
+sidebar_label: io
+---
+
+# alpha.dagger.io/io
+
+IO operations
+
+```cue
+import "alpha.dagger.io/io"
+```
+
+## io.#Dir
+
+Standard interface for directory operations in cue
+
+### io.#Dir Inputs
+
+_No input._
+
+### io.#Dir Outputs
+
+_No output._
+
+## io.#File
+
+Standard interface for file operations in cue
+
+### io.#File Inputs
+
+_No input._
+
+### io.#File Outputs
+
+_No output._
+
+## io.#ReadWriter
+
+Standard ReadWriter interface
+
+### io.#ReadWriter Inputs
+
+_No input._
+
+### io.#ReadWriter Outputs
+
+_No output._
+
+## io.#Reader
+
+Standard Reader interface
+
+### io.#Reader Inputs
+
+_No input._
+
+### io.#Reader Outputs
+
+_No output._
+
+## io.#Writer
+
+Standard Writer interface
+
+### io.#Writer Inputs
+
+_No input._
+
+### io.#Writer Outputs
+
+_No output._