Refactor plugin and README for documentation skills; add doc-docker and doc-funcs skills

skills/doc-docker/scripts/awk/find_col.awk

@@ -0,0 +1,8 @@
+!/^[[:space:]]*#/ && /  #/ {
+    idx = index($0, "  #")
+    content = substr($0, 1, idx - 1)
+    gsub(/ +$/, "", content)
+    col = length(content) + 2
+    if (col > max_col) max_col = col
+}
+END { print "max_col=" max_col }