docs: align Kubernetes, Go, and Liqo versions with what we actually support

[aryasoni98]

Problem

Documented runtime/tool versions are years behind CI and go.mod, and the Liqo tutorial cannot be followed on current Liqo.

Evidence

1. Kubernetes: README.md / Chart.yaml claim >= 1.21; CI tests v1.32 / v1.33 / v1.34 only. K8s 1.21 cannot satisfy Gateway API v1.6 CRDs used by the project.
2. Go: docs/local.md says Go 1.22.3; go.mod is go 1.26.5; CI uses go-version-file: ./go.mod.
3. Liqo: docs/liqo.md pins v0.5.4 docs and liqoctl generate peer-command (removed in 1.x; replaced by liqoctl peer). Also pins curlimages/curl:7.82.0.

Proposed fix

• Raise K8s floor in README + Chart.yaml to oldest version CI covers
• Point local.md Go install at go.mod (no hardcoded minor)
• Rewrite liqo.md for Liqo 1.x

Acceptance

Documented versions match CI / go.mod; Liqo tutorial steps work on current Liqo docs.

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Suggested label: documentation
Part of the v0.20.0 documentation audit.

[HYPERVAPOR]

I'd like to work on this issue.