fix typo errors for code and documentation

[pratikmota]

Changes:
Few typo/spelling error corrections in the .md documentation files and description of .go files.

1. an expecific -> a specific
2. inatance --> instance
3. delcare --> declare

Motivation:
To Improve Civo Terraform provider Golang code and documentation for community

[alejandrojnm]

The doc is created automatically by the release action, so there is not need to modify the doc files

[pratikmota]

Ok understood, generating documentation with terraform-plugin-docs. Thank you for reviewing.
I have reverted all changes of .md files. now only .go file changes are available for merging. Please let me know if any further suggestions. Thank you.