Renaming variables in notifyre.fish

[kaustubhhiware]

This is by far, the easiest task. The variable names in bash are standardised as seen here, but in fish they are not.

We just need to rename the variables in fish to the ones in shell, and update the README accordingly.

Fish is a language similar to shell, but designed for fish-shell (a different emulator), this task requires no understanding of fish or bash, just a basic understanding of variables in programming.