docs: add an enhancement proposal doc template (#1621)

Signed-off-by: feynmanzhou <[email protected]>

docs/proposals/proposal-doc-template.md

@@ -0,0 +1,37 @@
+# ORAS Enhancement Proposal Template
+
+An ORAS Enhancement Proposal (OEP) is a way to propose, communicate and coordinate on new features and enhancements for the `ORAS` project. It aims to provide a consistent format for proposing new features and improvements, ensures contributors follow a structured approach, making it easier for maintainers to review proposals.
+
+OEPs are suggested for most non-trivial changes. Specifically:
+
+- Anything that may be controversial
+- Most new features (except the small changes to existing flags or parameters)
+- Changes that are wide ranging or impact most of the project and users
+
+## Overview 
+
+> 1 – 2 sentences of what this document will outline.
+
+## Problem Statement & Motivation 
+
+> State the problem or challenge in a way that ties back to the target user. What are the goals and non-goals? Why does this matter to them? Make the problem real & relevant. We can link to an existing GitHub issue for clarification or justification.
+
+## Background & Context (Optional)
+
+> Clarify the background and context of this feature for users. Describes the broader landscape, including prior solutions and constraints.
+
+## Scenarios 
+
+> 3-4 sentences about what are the common user scenarios related to this feature.
+
+## Impact to Users and Ecosystem (Optional)
+
+> Provide data or insights with respect to the Problem Statement. Clarify how it benefits target users and the ecosystem.
+
+## Existing Solutions or Expectations (Optional) 
+
+> List the various ways in which a user may currently tackle this problem/challenge, or how is this feature supported by other tools in the industry. With what expectations will user approach our solution.
+
+## Proposal 
+
+> Proposed solution and alternative options. The desired user experience and CLI command operation can be included.