feat(experimental): add legend_isolate_on_click option

[maxim-yegorov]

Changes

New feature: legend_isolate_on_click

When enabled, clicking a legend item isolates that series (hides all others). Clicking the same item again restores all series.

type: custom:apexcharts-card
experimental:
  legend_isolate_on_click: true
series:
  - entity: sensor.living_room_temperature
    name: Living Room
  - entity: sensor.kitchen_temperature
    name: Kitchen

Requires all series to have unique names (same constraint as hidden_by_default). The default ApexCharts toggle behavior is disabled when this option is active.

Bug fix: TypeError crash in ApexCharts v5 sections view

Fixes TypeError: Cannot read properties of undefined (reading 'beforeMount') thrown when rendering charts in HA sections view (section_mode: true).

Root cause: ApexCharts v5 accesses chart.events.beforeMount unconditionally, but under certain config merging conditions chart.events ends up undefined.

Fix:

• Always include chart.events: {} in the layout config
• Add a defensive post-constructor guard before render()
• Patch ApexCharts v5.3.3 ESM via patch-package to add null-guards on chart.events accesses (beforeMount, mounted, updated, legendClick)

Test plan

• Enable experimental: { legend_isolate_on_click: true } on a multi-series chart
• Click a legend item — only that series should remain visible, others greyed out
• Click the same item again — all series restored
• Click a different item while one is isolated — isolation switches to the new item
• Verify no TypeError: beforeMount crash in sections view (section_mode: true)