Adding SemiBold to manual install instructions

Linux-instructions.md

@@ -58,7 +58,7 @@ else
     echo "Found fonts dir $fonts_dir"
 fi
 
-for type in Bold Light Medium Regular Retina; do
+for type in Bold Light Medium Regular Retina SemiBold; do
     file_path="${HOME}/.local/share/fonts/FiraCode-${type}.ttf"
     file_url="https://github.com/tonsky/FiraCode/blob/master/distr/ttf/FiraCode-${type}.ttf?raw=true"
     if [ ! -e "${file_path}" ]; then