Update README example to use actions/checkout@v5 (#62)

Author: omus

README.md

@@ -8,7 +8,7 @@ Julia needs to be installed before this action can run. This can easily be achie
 
 And example workflow that uses this action might look like this:
 
-```
+```yaml
 name: Run tests
 
 on: [push, pull_request]
@@ -26,7 +26,7 @@ jobs:
             julia-arch: x86
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.julia-version }}
@@ -68,4 +68,4 @@ If the registry contains private packages, or is itself private, the ssh protoco
 ...
 ```
 
-For Julia 1.7 and above, the `git_cli` option can be used to set the `JULIA_PKG_USE_CLI_GIT` [environment flag](https://docs.julialang.org/en/v1/manual/environment-variables/), for additional control of the SSH configuration used by `Pkg` to add/dev packages.
+For Julia 1.7 and above, the `git_cli` option can be used to set the `JULIA_PKG_USE_CLI_GIT` [environment flag](https://docs.julialang.org/en/v1/manual/environment-variables/), for additional control of the SSH configuration used by `Pkg` to add/dev packages.