--help doesn't mention line/column support

```
C:\> edit --help
Usage: edit [OPTIONS] [FILE]
Options:
    -h, --help       Print this help message
    -v, --version    Print the version number
```

but edit supports optional line and column info e.g. `edit foo.txt:123:45` opens foo.txt with the cursor at line 123 column 45. The help should say

```
Usage: edit [OPTIONS] [FILE[:LINE[:COLUMN]]]
```