Add a section about how to write scaler documentation (kedacore#545)

Co-authored-by: Tom Kerkhove <kerkhove.tom@gmail.com>
Signed-off-by: jorturfer <jorge_turrado@hotmail.es>

CONTRIBUTING.md

@@ -16,6 +16,7 @@ We provide easy ways to introduce new content:
 
 - [Adding new blog post](https://github.com/kedacore/keda-docs#adding-scaler-documentation)
 - [Adding new scaler documentation](https://github.com/kedacore/keda-docs#adding-scaler-documentation)
+- [Writing documentation for a scaler](https://github.com/kedacore/keda-docs#writing-documentation-for-a-scaler)
 - [Add new Frequently Asked Question (FAQ)](https://github.com/kedacore/keda-docs#add-new-frequently-asked-question-faq)
 - [Add new troubleshooting guidance](https://github.com/kedacore/keda-docs#add-new-troubleshooting-guidance)
 

README.md

@@ -119,6 +119,21 @@ This creates a boilerplate Markdown file in `content/docs/scalers/my-new-scaler.
 * `maintainer`
 * `description`
 
+## Writing documentation for a scaler
+
+In order to maintain the style consistency across different scalers, all the parameters which are listed have to be written using this convention:
+
+- name - Description. (Values: x, y, z, Default: y, Optional, Extra Info)
+
+If a parameter is required or doesn't have defined/default values, the missing info should be removed from the pattern.
+
+Here are a few examples:
+> - `targetMetricValue` - Target value for your metric.
+> - `metricFilter` - Aggregation method of the metric. (Values: `max`, `min`, `average`, `sum`, `variance`, Default: `average`, Optional)
+> - `metricPeriod` - Granularity of the metric. (Default: `300`, Optional)
+> - `subscriptionName` - Name of the Azure Service Bus queue to scale on. (Optional, Required when `topicName` is specified)
+
+
 ## Add new Frequently Asked Question (FAQ)
 
 To update the KEDA [FAQ page](https://keda.sh/docs/faq), update the TOML file at [`data/faq20.toml`]. Here's an example question/answer pair: