Add multiline example for input command (#16329)

# Description

Adds an example that documents how to use `input --reedline` to collect
multiple lines of input from the user

I also removed an extraneous and inconsistent space in the following
example.

# User-Facing Changes

Documentation addition

# Tests + Formatting

I did not run any tests or autoformatters because of the docs-only
nature of the change, and the fact that I copy-pasted the format from an
existing example. If the autoformatter is unhappy, I apologize.

# After Submitting

This PR should automatically update the docs site at the next release,
so no need to do anything there.

---------

Co-authored-by: Stefan Holderbach <sholderbach@users.noreply.github.com>

crates/nu-command/src/platform/input/input_.rs

@@ -218,9 +218,14 @@ impl Command for Input {
                 example: "let user_input = (input --default 10)",
                 result: None,
             },
+            Example {
+                description: "Get multiple lines of input from the user (newlines can be entered using `Alt` + `Enter` or `Ctrl` + `Enter`), and assign to a variable",
+                example: "let multiline_input = (input --reedline)",
+                result: None,
+            },
             Example {
                 description: "Get input from the user with history, and assign to a variable",
-                example: "let user_input = ([past,command,entries] | input )",
+                example: "let user_input = ([past,command,entries] | input --reedline)",
                 result: None,
             },
             Example {