Add documentation on how to contribute and re-write the README

README.md

@@ -1,16 +1,62 @@
-phpMyAdmin themes
-=================
+# phpMyAdmin themes
 
 Various contributed themes.
 
-Download
---------
+## Download
 
 Themes can be downloaded at <https://www.phpmyadmin.net/themes/>.
 
 
-Releasing
----------
+## How to contribute
 
-There is a script create-release.sh which creates zip with theme and optionally
-tags the repository and uploads it to the phpMyAdmin web site.
+### Get started
+
+- Go to the [phpmyadmin/themes](https://github.com/phpmyadmin/themes) repository
+- "Fork" the repository (see: [GitHub tutorial on how to fork a repository](https://docs.github.com/en/get-started/quickstart/fork-a-repo#forking-a-repository))
+- "Clone" your forked repository locally (see: [GitHub tutorial on how to clone a repository](https://docs.github.com/en/get-started/quickstart/fork-a-repo#cloning-your-forked-repository))
+
+### Updating/Creating themes
+
+If you already have the theme in your local phpMyAdmin folder, then delete the theme folder here and replace it with your local version (folder).
+
+For example:
+
+```sh
+rm -r /home/username/phpmyadmin/themes/mytheme
+cp -r /var/www/phpMyAdmin/themes/mytheme /home/username/phpmyadmin/themes/
+```
+
+#### Update the version
+
+Update "version" in `/home/username/phpmyadmin/themes/mytheme/theme.json` with the new version (of your theme).
+
+#### Create a branch and commit the changes
+
+Learn more about what is a commit: [here](https://github.com/git-guides/git-commit)
+
+For example:
+
+```sh
+# Go to the repository folder (your fork)
+cd /home/username/phpmyadmin/themes/
+# Create a new branch for your changes
+git checkout -b mytheme-version-x.y.z
+# Add your changes to git
+git add ./mytheme
+# Commit them
+git commit -m "[mytheme] version x.y.z"
+```
+
+#### Push the changes and open a pull-request
+
+Make the push:
+```sh
+git push
+```
+
+And then open a new pull-request: https://github.com/phpmyadmin/themes/pulls
+
+## Releasing
+
+There is a script `create-release.sh` which creates a zip file with the theme and optionally
+tags the git repository and uploads it to the phpMyAdmin website.