Document label and enum alignment values for EDGE components

[simonhamp]

What

Updates the mobile v4 EDGE component docs to reflect that alignment attributes now accept a readable label, a backing enum, or the raw integer — all three resolve to the same native value.

• layout.md — Replaces the integer-only alignment table with an explanation of the label / enum / integer options. Adds an "Underlying values" reference table (kept for anyone using the raw integers) and an "In PHP" section showing the Native\Mobile\Edge\Enums enums (AlignItems, AlignSelf, JustifyContent, TextAlign) used fluently.
• text.md — Documents text-align as left/center/right (label, TextAlign case, or 0/1/2) and updates the textAlign() signature to int|string|TextAlign.
• row.md — Example now uses AlignItems::Center instead of the magic number 1.
• icon.md — Blade examples use align-items="center" instead of :align-items="1".

Why

The previous docs only showed opaque integer values (:align-items="1", :justify-content="3"), which are hard to read and easy to get wrong. Surfacing the label and enum options makes the examples self-documenting while keeping the integer mapping available for reference.

Docs-only change; no application code touched.