Add `self-update` command for updating the binary

### Description
I like how `mago` manages self-updates:
```shell
mago self-update
```

It would be great if PHPantom could do this too.


### Use case
Run `phpantom_lsp self-update` for convenient updates.


### Proposed solution
Add a command for updating the `phpantom_lsp` binary:
```shell
phpantom_lsp self-update
```
