feat(directory): add ellipsis to truncated paths (#1563)

Adds ellipsis in front of truncated paths: …/
Configurable through new config option: directory.truncation_symbol
Fixes #1162, #1626

docs/config/README.md

@@ -651,6 +651,7 @@ it would have been `nixpkgs/pkgs`.
 | `disabled`          | `false`                                            | Disables the `directory` module.                                                 |
 | `read_only`         | `"🔒"`                                             | The symbol indicating current directory is read only.                            |
 | `read_only_style`   | `"red"`                                            | The style for the read only symbol.                                              |
+| `truncation_symbol` | `""`                                               | The symbol to prefix to truncated paths. eg: "…/"                                |
 
 <details>
 <summary>This module has a few advanced configuration options that control how the directory is displayed.</summary>
@@ -694,6 +695,7 @@ a single character. For `fish_style_pwd_dir_length = 2`, it would be `/bu/th/ci/
 
 [directory]
 truncation_length = 8
+truncation_symbol = "…/"
 ```
 
 ## Docker Context