🐛 Fix wrong assumption on external hover

[joao-m-santos]

📝 Description

Before, when trying to sync tooltips between two charts (like the example below), one of them would fly in instead of appear in the chart.

<lume-bar-chart
    v-bind="args"
    type="stacked"
    :hovered-index="hoveredIndex"
    @tooltip-opened="hoveredIndex = $event.index"
    @tooltip-moved="hoveredIndex = $event.index"
    @tooltip-closed="hoveredIndex = -1"
/>
<lume-bar-chart
    v-bind="args"
    type="stacked"
    :hovered-index="hoveredIndex"
    @tooltip-opened="hoveredIndex = $event.index"
    @tooltip-moved="hoveredIndex = $event.index"
    @tooltip-closed="hoveredIndex = -1"
/>

This was because the handleExternalHover in <lume-chart> was always calling handleInternalHover even if the external index was -1 (or null).

This PR corrects that into checking if it should handle it as show or hide tooltip based on the provided index.

💥 Is this a breaking change (Yes/No):

• [x] No
• [ ] Yes (please describe the impact and migration path for existing Lume users)

📝 Additional Information

• Added a Storybook Playground example of synced tooltips

Before submitting the PR, please make sure you do the following

• [x] Read the Contributing Guidelines.
• [x] Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• [x] Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• [x] Ideally, include relevant tests that fail without this PR but pass with it.

[netlify[bot]]

✅ Deploy Preview for adyen-lume ready!

Name	Link
🔨 Latest commit	7f7a4359e68380e5e58187234ed7fb04f98bcd94
🔍 Latest deploy log	https://app.netlify.com/sites/adyen-lume/deploys/6597d8f7fb2cb30008fd4482
😎 Deploy Preview	https://deploy-preview-383--adyen-lume.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.