Bump MSRV to 1.60 and check MSRV in CI (eupn#108)

* Bump MSRV to 1.60

syn 2.0.57 requires it.

```
error: failed to select a version for the requirement `syn = "=2.0.57"`
candidate versions found which didn't match: 2.0.56, 2.0.55, 2.0.54, ...
location searched: crates.io index
```

* Check MSRV in CI

Author: taiki-e

.github/workflows/ci.yml

@@ -28,3 +28,10 @@ jobs:
       - run: cargo test --manifest-path test-project/Cargo.toml -- --nocapture
 
       - run: cargo test --manifest-path test-procmacro-project/Cargo.toml -- --nocapture
+
+  msrv:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: taiki-e/install-action@cargo-hack
+      - run: cargo hack check --rust-version

Cargo.toml

@@ -3,7 +3,7 @@ name = "macrotest"
 version = "1.0.11" # remember to update in lib.rs
 authors = ["eupn <[email protected]>"]
 edition = "2018"
-rust-version = "1.56"
+rust-version = "1.60"
 license = "MIT OR Apache-2.0"
 readme = "README.md"
 repository = "https://github.com/eupn/macrotest"

README.md

@@ -2,14 +2,14 @@
 
 [![Travis-CI](https://api.travis-ci.com/eupn/macrotest.svg?branch=master)](https://travis-ci.com/eupn/macrotest)
 [![Crates.io](https://img.shields.io/crates/v/macrotest)](https://crates.io/crates/macrotest)
-![MSRV 1.56](https://img.shields.io/badge/MSRV-1.56-orange.svg)
+![MSRV 1.60](https://img.shields.io/badge/MSRV-1.60-orange.svg)
 [![docs.rs](https://docs.rs/macrotest/badge.svg)](https://docs.rs/macrotest/)
 [![Crates.io](https://img.shields.io/crates/d/macrotest)](https://crates.io/crates/macrotest)
 [![Crates.io](https://img.shields.io/crates/l/macrotest)](https://crates.io/crates/macrotest)
 
 Similar to [trybuild], but allows you to test how declarative or procedural macros are expanded.
 
-*Minimal Supported Rust Version: 1.56*
+*Minimal Supported Rust Version: 1.60*
 
 ----
 

src/lib.rs

@@ -5,7 +5,7 @@
 //!
 //! Similar to [trybuild], but allows you to write tests on how macros are expanded.
 //!
-//! *Minimal Supported Rust Version: 1.56*
+//! *Minimal Supported Rust Version: 1.60*
 //!
 //! <br>
 //!