feat(skill): add sample hero images and docs-sources reference

Four canonical hero image SVGs covering Kubernetes, Observability,
Platform Engineering, and Community palettes. These give the skill
a visual reference for the freeform-gradient glow style and Five
mascot treatment, so outputs can be calibrated against intent rather
than described from scratch.

Also adds docs-sources.md to the reference list in SKILL.md.

Signed-off-by: Lee Calcote <lee.calcote@layer5.io>

Author: leecalcote

.claude/skills/layer5-blog-writer/SKILL.md

@@ -129,4 +129,6 @@ darkthumbnail: ./hero-image.svg
 
 - **`references/blog-structure.md`** — Complete MDX format, frontmatter fields, all component patterns including `<MesheryDesignEmbed>` with the full table of available designs. Read before writing.
 - **`references/tags-categories.md`** — Approved tags and categories.
+- **`references/docs-sources.md`** — Local doc repo paths, URL mappings, and grep patterns for fact-checking.
 - **`scripts/generate_hero_image.py`** — Cosmic-style hero image generator.
+- **`assets/sample-hero-images/`** — Four canonical hero image examples showing the visual style, Five mascot treatment, and freeform glow across different category palettes (Kubernetes, Observability, Platform Engineering, Community). Use these as visual reference when deciding if an output looks right.