Adding a README.md file with dev-focused instructions (#4031)

* Adding a README.md file with dev-focused instructions

* Doc for version support policy

* Fix repository address

* Readme and changelog entries

* Fix version support policy typo

* Capitalizing titles and tool names

* Replacing functions with functionatilies

Author: wjrosa

README.md

@@ -0,0 +1,39 @@
+# WooCommerce Stripe Payment Gateway
+
+This is the official feature plugin for accepting payments via the Stripe payment gateway on a WooCommerce store.
+
+## Dependencies
+
+-   WooCommerce
+
+## Version Support Policy
+
+We adopt the L-2 version support policy for WordPress core strictly, and a loose L-2 policy for WooCommerce. See [more details](./docs/version-support-policy.md).
+
+## Development
+
+### Install Dependencies & Build
+
+-   `npm install`
+-   `composer install`
+-   `npm run build:webpack`, or if you're developing the client you can have it auto-update when changes are made: `npm start`
+
+If you run into errors with `npm install` it may be due to node version, try `nvm install` followed by `nvm use` then try again.
+
+When running the `composer install/update`, Composer may prompt you for a GitHub OAuth token before it can fetch the `subscriptions` and `pre-orders` extensions from GitHub.
+
+## Setup
+
+If you're using the Docker environment see setup instructions here:
+https://github.com/woocommerce/woocommerce-gateway-stripe/blob/trunk/docs/DOCKER.md
+
+Install the following plugins:
+
+-   WooCommerce
+-   Stripe Dev Tools (clone or download [the GitHub repo](https://github.com/woocommerce/woocommerce-gateway-stripe-dev-tools))
+
+## Debugging
+
+If you are following the Docker setup [here](https://github.com/woocommerce/woocommerce-gateway-stripe/blob/trunk/docs/DOCKER.md), Xdebug is ready to use for debugging.
+
+Install [Xdebug Helper browser extension mentioned here](https://xdebug.org/docs/remote) to enable Xdebug on demand.

changelog.txt

@@ -1,6 +1,7 @@
 *** Changelog ***
 
 = 9.3.0 - xxxx-xx-xx =
+* Dev - Adds a new README.md file to the plugin with specific development-focused instructions.
 * Add - Implements the Single Payment Element feature for the new checkout experience on the block checkout page.
 * Dev - Additional replacements for payment method constant values on the backend.
 * Fix - Improves the checking for existing customer attribute when retrieving a payment method that may be detached from a subscription.

docs/version-support-policy.md

@@ -0,0 +1,7 @@
+# Version Support Policy
+
+We have officially announced the L-2 version support policy for WooCommerce and WordPress core [since May 2021](https://developer.woocommerce.com/2021/05/12/woocommerce-payments-is-adopting-a-new-version-support-policy/).
+
+## What does this policy mean for contributors?
+
+As a contributor to WooCommerce Stripe Payment Gateway, you should be mindful when adding new features and functionalities to your PRs as your code needs to work within proper ranges of WordPress and WooCommerce versions. Although we have [a CI workflow](https://github.com/woocommerce/woocommerce-gateway-stripe/blob/develop/.github/workflows/compatibility.yml) to check the compatibility between the Stripe extension and these ranges, it's still good for contributors to be aware of this policy.

readme.txt

@@ -111,6 +111,7 @@ If you get stuck, you can ask for help in the [Plugin Forum](https://wordpress.o
 == Changelog ==
 
 = 9.3.0 - xxxx-xx-xx =
+* Dev - Adds a new README.md file to the plugin with specific development-focused instructions.
 * Add - Implements the Single Payment Element feature for the new checkout experience on the block checkout page.
 * Dev - Additional replacements for payment method constant values on the backend.
 * Fix - Improves the checking for existing customer attribute when retrieving a payment method that may be detached from a subscription.