README.md file updated

Closes #3349834

README.md

+# Field Compose
+
+This module provides a new Field Type which allows defining multiple fields in field settings with YAML based syntax and by respecting exactly the structure of
+[Form and render elements](https://api.drupal.org/api/drupal/elements).
+
+A good use-case for when to use it is if you have a component with multiple configuration options, e.g: a [slider library](https://glidejs.com/docs/options/) in which case you can avoid having 10+ addition tables(+revision tables) if you would implement normal fields for this purpose by storing values as JSON.
+
+With this approach, you might a expect slight increase in CPU usage as field values are decoded from JSON but this exactly what you might want as lots of time CPU is underused and DB operations are expensive(especially in a cloud env)
+
+## Requirements
+
+This module requires no modules outside of Drupal core.
+
+## Installation
+
+Install as you would normally install a contributed Drupal module. For further
+information, see
+[Installing Drupal Modules](https://www.drupal.org/docs/extending-drupal/installing-drupal-modules).
+
+## Configurations
+
+`-
+  id: my_bool
+  _type: checkbox
+  _title: Enable something
+-
+  id: my_string_field
+  _type: textfield
+  _title: Enter something(State dependent field)
+  _required: FALSE
+  _states:
+    visible:
+      :input[name="$field_name$[$field_item_delta$][my_bool]"]: { checked: true }`
+
+## Maintainers
+
+- hugronaphor - [hugronaphor](https://www.drupal.org/u/hugronaphor)
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