feat: add support for Capacitor 6 and 7

[robingenz]

What

Widens the supported Capacitor range from >=8.x.x to >=6.x.x.

• Declare @capacitor/core >=6.0.0 as a peer dependency (previously no Capacitor peer was declared at all).
• Update the compatibility table in the README and document that on Capacitor 6 and 7 the Capacitor CLI ignores the exit code of platform hooks, so errors during npx cap sync only surface in the log output (Capacitor 8 fails the command properly).
• Add CI e2e matrix jobs that run the full packaged-app test against Capacitor 6 and 7 (Ubuntu, Electron latest, Node 20 — the minimum version the example toolchain still supports).
• Widen the echo-plugin e2e fixture's peer dependency range accordingly.

Why

The platform never imports @capacitor/core at runtime — it couples only to Capacitor's contracts: the CLI platform-hook mechanism (capacitor:* scripts + CAPACITOR_* env vars) and the client bridge protocol (CapacitorCustomPlatform, PluginHeaders, nativePromise/nativeCallback). Both are unchanged between Capacitor 6.0, 7.0, and 8.0 (verified against the upgrade guides and diffs of the ionic-team/capacitor tags; the v7 breaking removals only affect legacy APIs this platform does not use).

Validated empirically: the packaged-app e2e suite (platform injection, plugin method round-trip via registerPlugin, events, error-code fidelity, appUrlOpen deep link) passes against Capacitor 6.2.1 and 7.6.7. The new CI jobs keep it that way.

Notes

• The vendor step is unaffected by the new peer dependency: it never traverses the platform package's own dependency closure, so packaged apps do not grow.
• The peer range is not capped at the top; the compatibility table remains the source of truth for tested majors.

[Copilot]

Pull request overview

This PR widens the supported Capacitor range for @capawesome/capacitor-electron to include Capacitor 6 and 7, aligns package metadata accordingly, and adds CI coverage to ensure the packaged-app e2e suite stays green across those supported majors.

Changes:

• Document compatibility as >=6.x.x and add a README note about Capacitor 6/7 CLI hook exit-code behavior.
• Declare @capacitor/core >=6.0.0 as a peer dependency (and widen the e2e echo-plugin fixture peer range similarly).
• Expand CI E2E to run additional Ubuntu jobs pinning Capacitor 6 and 7 (Node 20, Electron latest).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
README.md	Updates compatibility table and adds note about Capacitor 6/7 hook exit-code handling.
package.json	Adds @capacitor/core >=6.0.0 peer dependency to reflect supported range.
example/local-plugins/echo/package.json	Widens fixture peer dependency range to match supported Capacitor majors.
.github/workflows/ci.yml	Adds E2E matrix include entries to run packaged-app tests against Capacitor 6 and 7.

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