[feature request] Make `navi` variables to `fzf`'s `header` option about navi HOT 3 OPEN

# add submodule
git submodule add <is_branch>

$ is_branch: echo "" --- --map "grep -Pq '.+' && echo 'branch=<is_branch>'" --header "are you adding submodule from a specific branch? Type the branch name if yes, or leave empty if no."

# add submodule
git submodule add <prefix><is_branch>

$ is_branch: echo "" --- --header "are you adding submodule from a specific branch? Type the branch name if yes, or leave empty if no."
$ prefix: [[ -n $(echo <is_branch>) ]] && echo '--branch=' || echo '' --- --fzf-overrides '-1'

% sed

# Print a specific line from a file
sed -n <number>p <file>

$ file: find . -maxdepth 1 -type f | cut -c3-
$ number: aux=$(wc -l <file> | cut -f 1) && echo "This file contains $aux pages" --- --header-lines 1

% sed

# Print a specific line from a file
sed -n <number>p <file>

$ file: find . -maxdepth 1 -type f | cut -c3-
$ number: export aux=$(wc -l <file> | cut -d ' ' -f 1) --- --header "The file <file> contains $aux pages "