Add a 'Donate' / 'Support development' link in Settings

[gek0z]

Summary

Add a row in Settings pointing to a donation page so users who want to chip in toward YouMenuTube's upkeep have a discoverable way to do so.

Proposed placement

Inside the existing Section("About") in Sources/Views/SettingsView.swift, sibling to the version / update rows. A SwiftUI Link with a heart icon:

Link(destination: URL(string: "<donation-url>")!) {
    Label("Support development", systemImage: "heart.fill")
        .symbolRenderingMode(.hierarchical)
        .foregroundStyle(.pink)
}
.font(.caption)

Prerequisite — pick a platform

This issue depends on deciding where donations should go. Options:

• GitHub Sponsors — zero fees, same domain as the repo, also enables the "Sponsor" button on the repo page via .github/FUNDING.yml. Likely the best fit for a GitHub-hosted open-source project.
• Buy Me a Coffee / Ko-fi — lower friction for casual one-off tips, no GitHub account needed.
• PayPal.me — universal but takes a cut and feels less developer-native.

Recommendation: set up GitHub Sponsors, add .github/FUNDING.yml, and use that URL in the Settings link.

Acceptance

• .github/FUNDING.yml committed so the "Sponsor" button shows up on the repo.
• SettingsView.swift has a visible donation row that opens the chosen URL in the user's default browser.
• README links to the same donation page in an appropriate spot (e.g. next to the license).

Out of scope

• In-app purchases / IAP (Apple cut doesn't make sense here).
• Any tip-jar UI beyond one link.