Committing LIF_TShirt_Sizing.md to /docs

LIFTShirtSizing.md for review to upload to docs folder of GH.

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Author: Jennifer-Oxborough

docs/LIF_TShirt_Sizing.md

@@ -0,0 +1,26 @@
+**T-Shirt Sizing Guidelines**
+
+This project uses t-shirt sizing to describe the relative scope and complexity of work items.
+
+**Important:**  
+T-shirt sizes do **not** represent time, hours, or delivery estimates.  
+They are intended to help contributors understand scope and help maintainers prioritize work.
+
+Sizing is based on:
+
+* Functional change  
+* Surface area of the codebase affected  
+* Risks and unknowns  
+* Required system understanding
+
+**Size Definitions:**
+
+| Size | Description |
+| :---- | :---- |
+| XS | Very small change with minimal impact (comments, configuration tweaks, typos). |
+| S | Small, self-contained change affecting a single function or component with low risk. |
+| M | Moderate change introducing new behavior within an existing module or feature area. |
+| L | Larger change spanning multiple components, modules or interfaces.  May require coordination or design discussion. |
+| XL | Significant change affecting architecture, data models, APIs, or core workflows.  High risk or uncertainty. |
+| XXL | Foundational or systemic change (major refactor, redesign, or new subsystem).  Requires design review before implementation. |
+