Update install instructions from to `go install`
Looks like `go get` has been deprecated.
New method for installation is `go install <repo-url>@latest`
In this case:
```sh
go install github.com/qeesung/image2ascii@latest
```
@@ 15,7 15,7 @@ Image2ASCII is a library that converts images into ASCII images and provides com## Installation
```bash
-go get github.com/qeesung/image2ascii
+go install github.com/qeesung/image2ascii@latest
```
## CLI usage