feat(username): add detect_env_vars as option (#5833)

* Added the option "detect_env_vars" to the `username` module

with the same functionality as in the `hostname` module.

* Fixed logic error and added test to catch it

* build(deps): update dependency vitepress to ^1.0.0-rc.45

* build(deps): update rust crate shadow-rs to 0.27.1

* Added the option "detect_env_vars" to the `username` module

with the same functionality as in the `hostname` module.

* Fixed logic error and added test to catch it

* Removed unused gix import

* Removed unused gix import, again

* Removed unused gix import. Next try

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/config-schema.json

@@ -1717,6 +1717,7 @@
     },
     "username": {
       "default": {
+        "detect_env_vars": [],
         "disabled": false,
         "format": "[$user]($style) in ",
         "show_always": false,
@@ -5878,6 +5879,13 @@
     "UsernameConfig": {
       "type": "object",
       "properties": {
+        "detect_env_vars": {
+          "default": [],
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        },
         "format": {
           "default": "[$user]($style) in ",
           "type": "string"