Update issue templates (#305)

Author: voltur01

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,26 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: bug
+assignees: ''
+
+---
+
+**Summary**
+[A clear and concise description of what the bug is]
+
+**To Reproduce**
+1. [Steps to reproduce]
+
+**Expected behavior**
+[A clear and concise description of what you expected to happen]
+
+**Actual behavior**
+[A clear and concise description of what happens instead]
+
+**Environment**
+[Arm Toolchain variant and version, host OS: name, version, architecture]
+
+**[Additional context]**
+[Optional: Add any other context about the problem here or remove]

.github/ISSUE_TEMPLATE/downstream-change.md

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+---
+name: Downstream Change
+about: Issue to track a Downstream Change
+title: "[Downstream Change] "
+labels: downstream-change
+assignees: ''
+
+---
+
+**What is the change**
+[Describe the change here, see CONTRIBUTING.md for details]
+
+**Why this change cannot be done upstream**
+[Provide the rationale]

.github/ISSUE_TEMPLATE/feature_request.md

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+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: enhancement
+assignees: ''
+
+---
+
+**Problem or Opportunity**
+[A clear and concise description of what the problem or opportunity to improve is]
+
+**Requested Solution**
+[A clear and concise description of what you want to happen]
+
+**Alternatives Considered**
+[A clear and concise description of any alternative solutions or features you've considered]
+
+**Additional context**
+[Add any other context or screenshots about the feature request here]

.github/ISSUE_TEMPLATE/rfc.md

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+---
+name: RFC
+about: Request for Comments (RFC)
+title: ''
+labels: RFC
+assignees: ''
+
+---
+
+**Summary**
+[A short summary/abstract of what this RFC is about so that readers can quickly judge if they are interested in going into the details or not]
+
+**Background**
+[Provide the context: relevant current status and/or history, references to more information]
+
+**Problem (or Opportunity or Goals)**
+[Clearly state the problem to solve or the opportunity (goals) to make use of, if this more an improvement/innovation.]
+
+**[Out of Scope]**
+[Optional: In cases where people could naturally have expectations/misconceptions about the solution, clearly state what this RFC is not about]
+
+**Proposal**
+[Explain and provide relevant details of the actual proposed design or actions]
+
+**[Benefits]**
+[Optional: Highlight why the proposal makes sense, especially if this is not a problem solving, but exploiting an opportunity]
+
+**[Implementation or Transition]**
+[Optional: Some solutions may need multiple steps to be implemented or require migration/transition period from the previous approach - outline the plan here]
+
+**[Risks]**
+[Optional: Consider risks and mitigations, if relevant]
+
+**Alternatives**
+[Explain what alternatives exist or were evaluated and rejected, why]
+
+**[Request for Comments]**
+[Optional: If it is not obvious, specifically list what questions/insights are asked from reviewers]