Chore: Add issues for advanced features

[wenley]

Advanced Features currently declared as unsupported:

• Output redirection
• Manual reading additional lines
• Rare Built-in Functions (e.g. Time, Bitwise operators) - see https://www.gnu.org/software/gawk/manual/html_node/Built_002din.html
• From-Until patterns

[wenley]

Many many many built-in String functions: https://www.gnu.org/software/gawk/manual/html_node/String-Functions.html

[wenley]

Made a fresh batch of tickets. These will constitute a v1.1

[wenley]

Made another batch of tickets for v1.2.

This ticket is now just a placeholder for planned-unsupported features.