docs: fix malformed YAML row and missing blank line before `---` in README

[Suknna]

Summary

Two Markdown formatting bugs in README.md, both in the "Supported languages" / YAML area.

1. YAML table row is malformed (5 cells instead of 7)

The table header has 7 columns (Language | Outline | Edit | AST | Semantic | Imports | Refactor), but the YAML row only has 5 cells:

| YAML (incl. Kubernetes) | ✓ | ✓ | — | — |

This breaks the row's rendering and misaligns it with the rest of the table. It also uses —, which is inconsistent with the table convention where an empty cell means "unsupported".

Based on the body text ("YAML files are semantically indexed"), the row should mark Semantic as supported:

| YAML (incl. Kubernetes) | ✓ | ✓ | | ✓ | | |

2. Missing blank line before horizontal rule

The "YAML / Kubernetes / CRDs." paragraph is immediately followed by --- with no blank line in between:

...falls back to top-level keys as symbols.
---

Without a blank line, CommonMark renders the --- as a setext heading underline, turning the entire preceding paragraph into a heading instead of producing a horizontal rule. A blank line is required.

Environment

• File: README.md
• Affected lines: ~176 and ~185-186 (current main)