chore(mdx support): added altered CONTRIBUTING file from .md to .mdx

CONTRIBUTING.mdx

@@ -0,0 +1,47 @@
+### Local Development
+
+This project builds with node version:
+
+{/* CODEBLOCK_START {"value": ".nvmrc", "hideValue": true} */}
+{/* prettier-ignore */}
+~~~~~~~~~~bash
+v20.10.0
+~~~~~~~~~~
+
+{/* CODEBLOCK_END */}
+
+After cloning the repository, install dependencies and build the project:
+
+```
+npm ci
+```
+
+Build the library and watch for changes:
+
+```
+npm start
+```
+
+Link your local copy:
+
+```
+npm link
+```
+
+`markdown-inject` commands in any terminal will now run using your local copy.
+
+### Validation
+
+This app ships with a local suite of [jest](https://jestjs.io/) tests, [eslint](https://eslint.org/) + [prettier](https://prettier.io/) configurations for code consistency and formatting, and [TypeScript](https://www.typescriptlang.org/) type validation. Each of these features can be validated using...
+
+```bash
+npm test
+npm run lint
+npm run build
+```
+
+A `validate` utility script chains these calls together, and is called on every commit.
+
+```bash
+npm run validate
+```