Allow CTA message override from _config.yml file

[pepinho24]

Currently, the CTA messages are all stored in the /_data/cta_panels_data.yml file and a change to the message requires a PR and approval from the repo owners.

• https://github.com/telerik/docs-seed/commits/master/_data/cta_panels_data.yml

Describe the solution you'd like
One possible solution would be to change the logic to check for a CTA_message property in the _config.yml, and that does not exist, only then to fall back to the message in cta_panels_data.yml.

This will allow each team to control the CTA text without the need to change the data in the docs-seed repository.

[pepinho24]

To override the CTA panels data that comes from https://github.com/telerik/docs-seed/blob/master/_data/cta_panels_data.yml, you can define the new values in the _config.yml under the cta_panels_data_overwrites property.

You are not obligated to overwrite all the data available in the _data/cta_panels_data, so you can overwrite only the properties you need. The example below shows how to change only the message shown in the CTA panels on Introduction and Overview articles.

## CTA panels on every page for trials
has_cta_panels: true

cta_panels_data_overwrites:
   message: "professional grade UI library with 90 native components for building modern and feature-rich applications."