Merge pull request #16 from PrestaShop/doc

Add documentation

README.md

@@ -1,3 +1,47 @@
 # contextual-help-api
 
-API that parses content from PrestaShop User documentations, formats it and serves it to be used inside PrestaShop back-office
+## About
+
+This webapp is in charge of providing the documentation that is displayed in PrestaShop's back-office.
+That's the application behind https://help.prestashop-project.org/
+
+### How it works?
+
+When a request is made to this app, the returned documentation is taken from the user documentation's Github repository,
+parsed, and converted to either plain HTML or json-encoded HTML.
+
+Which content from which repository to be taken is related to the request path and/or parameters that indicates PrestaShop's version,
+language and back-office page the documentation is needed for.
+
+There's basically 2 ways you can make request to this app:
+
+- http​s://this.app/api/?request=getHelp%3D**page_controller**%26version%3D**prestashop_version**%26language%3D**lang_iso_code**%26callback%3D**jsonp_callback**
+- http​s://this.app/**lang_iso_code**/doc/**page_controller**/?version=**prestashop_version**
+
+In the first case, the part after `?request=` is actually urlencoded. By using this way, a jsonp response containing the HTML documentation will be returned.
+
+In the second case, the documentation is returned as plain HTML.
+
+### Configurations
+
+The repositories where the documentation is taken from are defined in `config/mapping_urls.yml`.
+The markdown files to be used are defined in `config/mapping_v{prestashop_version}`.
+
+### Markown + Liquid tags
+
+As the markdown available in the user documentation repositories is made through Gitbook, there's some parts that are not classic markdown.
+Those specials features are more or less [liquid tags](https://jekyllrb.com/docs/liquid/tags/) and a special Markdown parsing/rendering extension has been
+made to handle them (`src/Markdown/Node/Liquid.php`, `src/Markdown/Parser/Block/LiquidBlock*` and `src/Markdown/Renderer/*`).
+
+## Requirement
+
+PHP >= 8.0.7
+
+## How to run it
+
+### Locally
+
+```shell
+$ composer install
+$ php -S localhost:8080 -t public/
+```