fix: readFile on windows (works cross-platform) (#1)

Using path instead of filepath fixes an issue on Windows where the
template files could not be found. I tested these changes on macOS and
Windows and they worked for me.

## Relevant docs:

### https://pkg.go.dev/embed

```
...
The path separator is a forward slash, even on Windows systems.
...
```

### https://pkg.go.dev/path/filepath
```
The filepath package uses either forward slashes or backslashes, depending on the operating system. To process paths such as URLs that always use forward slashes regardless of the operating system, see the [path](https://pkg.go.dev/path) package.
```

Author: joshuaslate

util.go

@@ -2,13 +2,13 @@ package yaakcli
 
 import (
 	"os"
-	"path/filepath"
+	"path"
 	"strings"
 )
 
-func writeFile(path, contents string) {
-	CheckError(os.MkdirAll(filepath.Dir(path), 0755))
-	CheckError(os.WriteFile(path, []byte(contents), 0755))
+func writeFile(writePath, contents string) {
+	CheckError(os.MkdirAll(path.Dir(writePath), 0755))
+	CheckError(os.WriteFile(writePath, []byte(contents), 0755))
 }
 
 func readFile(path string) string {
@@ -18,9 +18,9 @@ func readFile(path string) string {
 }
 
 func copyFile(relPath, dstDir, name string) {
-	contents := readFile(filepath.Join("template", relPath))
+	contents := readFile(path.Join("template", relPath))
 	contents = strings.ReplaceAll(contents, "yaak-plugin-name", name)
-	writeFile(filepath.Join(dstDir, relPath), contents)
+	writeFile(path.Join(dstDir, relPath), contents)
 }
 
 func fileExists(path string) bool {