Make more user friendly snippets

[EmilyGraceSeville7cf]

• make snippet descriptions more user-friendly
• add more snippets for conditions and loops
• remove some snippets for expansion, default to sed when possible
• remove yq snippets, default to jq
• remove snippets for character classes (I think they are not required)
• add more snippets for variable declarations
• add snippets for quick string/byte filtering
• add snippet for completion

Snippets made similar to Fish ones.