dev: simplify placeholder syntax, make consistent with other repository template

Cargo.toml

···
 resolver = "3"
 
 [workspace.package]
-authors = ["{{author}} <{{email}}>"]
+authors = ["_author_ <_email_>"]
 license = "MIT OR Apache-2.0"
 edition = "2024"
 rust-version = "1.91.0"

LICENSE-MIT

···
 MIT License
 
-Copyright (c) 2026 {{author}}
+Copyright (c) 2026 _author_
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

···
 
 ### Replace placeholders
 Replace the following placeholders with your editor's find-and-replace:
-- `{{library}}` - The name of the library.
-- `{{desc}}` - The description of the library.
-- `{{author}}` - The author's name of the library. For example, this could be a username, nickname, or real name.
-- `{{email}}` - The author's email address. This is optional and can be deleted.
+- `_library_` - The name of the library.
+- `_desc_` - The description of the library.
+- `_author_` - The author's name of the library. For example, this could be a username, nickname, or real name.
+- `_email_` - The author's email address. This is optional and can be deleted.
 - `my_crate` - Replace this with the name of your crate.
 
 ## Configure

crates/my_crate/Cargo.toml

···
 name = "my_crate"
 publish = false
 version = "0.1.0"
-description = "{{desc}}"
+description = "_desc_"
 include = ["src", "LICENSE*"]
 keywords = []
 categories = []

crates/my_crate/README.md

···
-# {{library}}
+# _library_
 [![License][license-badge]][license-url]
 
 [license-badge]: https://img.shields.io/badge/License-MIT%20%26%20Apache%202.0-blue?style=flat-square
 [license-url]: #license
 
-{{desc}}
+_desc_
 
 ## Install
 ```shell
-cargo add {{library}}
+cargo add _library_
 ```
 
 ## License