Create new content type programmatically using Configuration API

Module Name = my_module

Content Type = my_new_content

Create content type

Put this two files into my_module/config/install/

# File 1 

# node.type.my_new_content.yml

langcode: en

status: true

dependencies:

  enforced:

    module:

      - my_module

name: 'My New Content'

type: my_new_content

description: 'Content type that can be used to provide <em>Test content</em>'

help: ''

new_revision: false

preview_mode: 1

display_submitted: true

Add existing field

# File 2

#field.field.node.my_new_content.body.yml

langcode: en

status: true

dependencies:

  config:

    - field.storage.node.body

    - node.type.my_new_content

  module:

    - text

id: node.my_new_content.body

field_name: body

entity_type: node

bundle: my_new_content

label: 'Message Body'

description: 'Content of the new CT'

required: false

translatable: true

default_value: {  }

default_value_callback: ''

settings:

  display_summary: true

field_type: text_with_summary

Create a field configuration file

Step 1.    Create the field from the user interface.

Step 2. Export to a file from /admin/config/development/configuration/single/export

        Field Storage (then Field) and Select your field (Here node.field_my_test_text)

        Copy name ftom the bottom of the textarea (Ex: field.storage.node.field_my_test_text.yml)

        Create a config file (Here field.storage.node.field_my_test_text.yml) on /config/install

        Copy the text except 'uudd' line

Step 3. Install or Update your module

        If update, follow update procedure of this tutorial.

Update a Field instance.

Step 1. Update yml file.

Step 2. Create an update in my_module.install , like:

function my_module_update_8001() {

  $config_path = drupal_get_path('module', 'my_module') . '/config/install/field.field.node.my_new_content.body.yml';

  $data = \Symfony\Component\Yaml\Yaml::parse($config_path);

  \Drupal::configFactory()

    ->getEditable('field.field.node.my_new_content.body')

    ->setData($data)

    ->save(TRUE);

  return 'The Field has been updated.';

}

Creating a custom content type in Drupal 8

Tuto : https://www.drupal.org/node/2629550

Creating a content entity type in Drupal 8

https://www.drupal.org/node/2192175