[Bug]: Make clear errors on which variable names we cant use

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Description of the bug

Currently we cant use some vars like ref or class as they are reserved C# keywords, so we need make clear in errors on which variable names we cant use

Reproduction steps

just try to set ref as var and use it

What is the current bug behavior?

.

What is the expected correct behavior?

.

Version of the client

v0.3.1.2637

Type of client

Web client

Environment

- OS:Win
- Virtualization: None
- Browser: Chrome

OpenBullet2 logs

No response

Client / Browser logs

No response

Relevant screenshots or videos

No response

Relevant LoliCode if needed

No response

Additional information

No response