feat(icons): add square-text (#4609)

* feat(icons): add square-text

Adds square-text: a solid square containing three ragged lines of text.

The set has square-dashed-text but no solid-border equivalent, which is
the same asymmetry solid/dashed pairs elsewhere avoid. This reuses
square-dashed-text's exact text glyph (M7 8h8 / M7 12h10 / M7 16h6) on the
standard 18x18 rx=2 square, so it reads as the solid twin.

Distinct from square-menu, whose lines are equal full-width (a menu, not
running text).

* chore(icons): expand square-text tags and fill use-cases

Applies the metadata bot's tag suggestions (curated) and fills the
use-cases field.

* chore(icons): promote lab/text-square to square-text

Per review on #4609: square-text is identical to lab/text-square, so
this removes the lab entry and merges its metadata (tags + development
category) into the promoted icon.

* chore(icons): credit danielbayley and expand square-text use-cases

Per review on #4609: adds @danielbayley (original author of lab/text-square)
to contributors, and expands use-cases per @ericfennis.

lab/text-square.json

@@ -1,19 +0,0 @@
-{
-  "$schema": "../icon.schema.json",
-  "tags": [
-    "note",
-    "log",
-    "document",
-    "page",
-    "paper",
-    "sheet",
-    "list",
-    "script",
-    "code",
-    "editor"
-  ],
-  "categories": [
-    "text",
-    "development"
-  ]
-}

lab/text-square.svg

@@ -1,16 +0,0 @@
-<svg
-  xmlns="http://www.w3.org/2000/svg"
-  width="24"
-  height="24"
-  viewBox="0 0 24 24"
-  fill="none"
-  stroke="currentColor"
-  stroke-width="2"
-  stroke-linecap="round"
-  stroke-linejoin="round"
->
-  <rect width="18" height="18" x="3" y="3" rx="2" />
-  <path d="M7 12h10" />
-  <path d="M7 16h6" />
-  <path d="M7 8h8" />
-</svg>