[Tools] Check for non-ASCII

[mitiko]

https://pages.cs.wisc.edu/~markm/ascii.html

Add other encodings maybe:

• UTF-8
• UTF-16

[mitiko]

Nice to have:

• list of characters to allow (input as a text field?)
• groups of characters to allow (cyrillic, digits, capital letters, lowercase letters, etc)
• do not choke on big inputs & many disallowed characters (like the reference page)