Add illegal characters to schema linter

[ESapenaVentura]

Description

To avoid the use of illegal characters in the schema, I would like to update the schema linter so that it highlights characters that should not be used (e.g., "`")

An example of why this could be useful can be found in this PR: #1499

Acceptance Criteria

• A list of illegal chars is defined
• The schema linter has been updated to catch these characters