Issue formatting guide for Guideline Form (#183)

* Create issue-formatting-guide.md

* Clarification

* Clarification

* Clarification

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Co-authored-by: Pete LeVasseur <[email protected]>

Author: x0rw

docs/issue-formatting-guide.md

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+# Issue Formatting Guide
+
+## Purpose
+This guide outlines Markdown standards when submitting a [Coding Guideline issue template](https://github.com/rustfoundation/safety-critical-rust-coding-guidelines/issues/new?template=CODING-GUIDELINE.yml).
+
+We follow these rules to ensure our content converts cleanly from Markdown to reStructuredText (.rst) when an Issue converted to a Pull Request. During that process the [m2r](https://pypi.org/project/m2r/) converter is used, which is then fed into Sphinx for documentation.
+
+---
+
+## Supported formatting (does not break conversion from Issue => Pull Request)
+- **Bold** for emphasis or labels (`**Important Note**`).
+- *Italics* for a single word or phrase (`*Warning*`).
+- `inline code` for identifiers and short tokens (`cargo build`).
+- Simple unordered lists:
+    - Item 1
+    - Item 2
+- Simple ordered lists:
+    1. First step
+    2. Second step
+
+
+- Tables with basic content:
+
+| Header 1 | Header 2 | Header 3 |
+|----------|----------|----------|
+| Row 1 Col 1 | Row 1 Col 2 | Row 1 Col 3 |
+| Row 2 Col 1 | Row 2 Col 2 | Row 2 Col 3 |
+
+- Links with clear, simple syntax: `[link text](https://example.com)`.
+- Simple blockquotes: `> This is a quote.`.
+
+---
+## Unsupported formatting (breaks conversion from Issue => Pull Request)
+
+The following types of formatting are not currently supported in the bodies of text submitted. This may change in the future if we find ways to support them.
+
+- **Nested formatting:** Combining different formatting styles, like **bold around `inline code`**, is unreliable.
+- **Markdown headings:** Using `#`, `##`, or `###` conflicts with Sphinx's heading structure.
+- **Complex lists:** Lists with inconsistent indentation or mixed bullet types often fail.
+    - Example:
+    ```
+    - A list item
+      - Another sub-item
+       1. A nested list.
+    ```
+- **Complex tables:** Tables with merged cells, multi-line content, or rich/nested formatting will likely break.
+- **Standalone horizontal rules:** Using `---` or `***` will be misinterpreted.