fix(ui): add slot for dropdown button in split mode #16955

[SamVanini]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Documentation
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested on a Cordova (iOS, Android) app
• It's been tested on an Electron app
• Any necessary documentation has been added or updated in the docs or explained in the PR's description.

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to start a new feature discussion first and wait for approval before working on it)

Other information:
The following PR adds a slot to the dropdown button of QBtnDropdown component, when split prop is used. This change allows to customize even this button, enabling the user to add tooltips or other accessibility related attributes

To clarify and document this new slot I updated the docs section, providing a practical example using the one available for label slot usage as blueprint

Fix #16955

[github-actions]

UI Tests Results

    1 files     98 suites   47s ⏱️
1 031 tests 1 031 ✅ 0 💤 0 ❌
1 050 runs  1 050 ✅ 0 💤 0 ❌

Results for commit e34c90d.

♻️ This comment has been updated with latest results.

[github-actions]

Build Results

JSON API

📜 Changes detected:

diff --git a/./current-build/api/QBtnDropdown.json b/./pr-build/api/QBtnDropdown.json
index 7eb266b..60c7e98 100644
--- a/./current-build/api/QBtnDropdown.json
+++ b/./pr-build/api/QBtnDropdown.json
@@ -478,6 +478,9 @@
     "loading": {
       "desc": "Override the default QSpinner when in 'loading' state",
       "addedIn": "v2.8"
+    },
+    "arrow-container": {
+      "desc": "Customize arrow container button's content when using 'split' prop"
     }
   },
   "events": {

Types

📜 Changes detected:

diff --git a/./current-build/types/index.d.ts b/./pr-build/types/index.d.ts
index 28ddad9..77dc77f 100644
--- a/./current-build/types/index.d.ts
+++ b/./pr-build/types/index.d.ts
@@ -4176,6 +4176,10 @@ export interface QBtnDropdownSlots {
    * Override the default QSpinner when in 'loading' state
    */
   loading: () => VNode[];
+  /**
+   * Customize arrow container button's content when using 'split' prop
+   */
+  "arrow-container": () => VNode[];
 }
 
 export interface QBtnDropdown extends ComponentPublicInstance<QBtnDropdownProps> {