Add missing edition

[Rustin170506]

When I read this doc, I found that we are missing the edition key in this manifest. I think we should add it because cargo new always does this.

[rust-highfive]

r? @ehuss

(rust-highfive has picked a reviewer for you, use r? to override)

[epage]

@bors r+

[bors]

📌 Commit 96bf10e has been approved by epage

It is now in the queue for this repository.

[bors]

⌛ Testing commit 96bf10e with merge b1b25a0...

[weihanglo]

Should we document the process of updating edition field throughout Cargo book?

cargo/src/cargo/core/features.rs

Lines 136 to 149 in a6e72d0

	/// ## Stabilization instructions
	///
	/// - Set [`LATEST_UNSTABLE`] to None.
	/// - Set [`LATEST_STABLE`] to the new version.
	/// - Update [`is_stable`] to `true`.
	/// - Set the editionNNNN feature to stable in the [`features!`] macro invocation below.
	/// - Update any tests that are affected.
	/// - Update the man page for the `--edition` flag.
	/// - Update unstable.md to move the edition section to the bottom.
	/// - Update the documentation:
	/// - Update any features impacted by the edition.
	/// - Update manifest.md#the-edition-field.
	/// - Update the `--edition` flag (options-new.md).
	/// - Rebuild man pages.

[bors]

☀️ Test successful - checks-actions
Approved by: epage
Pushing b1b25a0 to master...

[Rustin170506]

Should we document the process of updating edition field throughout Cargo book?

cargo/src/cargo/core/features.rs

Lines 136 to 149 in a6e72d0

	/// ## Stabilization instructions
	///
	/// - Set [`LATEST_UNSTABLE`] to None.
	/// - Set [`LATEST_STABLE`] to the new version.
	/// - Update [`is_stable`] to `true`.
	/// - Set the editionNNNN feature to stable in the [`features!`] macro invocation below.
	/// - Update any tests that are affected.
	/// - Update the man page for the `--edition` flag.
	/// - Update unstable.md to move the edition section to the bottom.
	/// - Update the documentation:
	/// - Update any features impacted by the edition.
	/// - Update manifest.md#the-edition-field.
	/// - Update the `--edition` flag (options-new.md).
	/// - Rebuild man pages.

But I think we have the edition guidebook.