Make contribution guidelines more accessible (#17)

Moves the file to the root of the project, adds a .md extension and
links to it from the webpage.

README.md

@@ -4,7 +4,7 @@ An index of applications built for the nRF Connect SDK.
 
 ## Contributing
 
-If you or your organization has a project that you'd like to include in the nRF Connect SDK App Index, you can open a pull request against this repository. See the details shown in the [`CONTRIBUTING`](.github/CONTRIBUTING) file for more information.
+If you or your organization has a project that you'd like to include in the nRF Connect SDK App Index, you can open a pull request against this repository. See the details shown in the [`CONTRIBUTING`](./CONTRIBUTING.md) file for more information.
 
 ## Development
 

site/src/app/AboutDialog.tsx

@@ -48,7 +48,14 @@ export default function AboutDialog(props: { close: () => void }): JSX.Element {
                     <H2>Contributing</H2>
                     <P>
                         If you've developed an application or sample, you can apply to have it
-                        listed in this index.
+                        listed in this index. Read the{' '}
+                        <a
+                            className="text-blue-800"
+                            href="https://github.com/nrfconnect/ncs-app-index/blob/main/CONTRIBUTING.md"
+                        >
+                            contribution guidelines
+                        </a>{' '}
+                        for details.
                     </P>
                 </div>
             </div>