Feat: Window specific separator config

[mklbravo]

This pull request:

• [x] Add window_type to build_window_format
• [x] If window specific separator is configured it will override global configuration
• [x] Update README.md to reflect new available options

Allowed new configuration options:

# Current type window configuration. If set, it will override the global configuration
set -g @catppuccin_window_current_left_separator "█"
set -g @catppuccin_window_current_middle_separator " 󰿟 "
set -g @catppuccin_window_current_right_separator "█"

# Default type window configuration. If set, it will override the global configuration
set -g @catppuccin_window_default_left_separator "█"
set -g @catppuccin_window_default_middle_separator " 󰿟 "
set -g @catppuccin_window_default_right_separator "█"

Fixes #197

[mklbravo]

This theme can be configured like this:

# Window global configuration
set -g @catppuccin_window_left_separator "█"
set -g @catppuccin_window_middle_separator "█ "
set -g @catppuccin_window_number_position "left"
set -g @catppuccin_window_right_separator "█"

# Window current configuration
set -g @catppuccin_window_current_middle_separator " 󰿟 "
set -g @catppuccin_window_current_fill "all"

# Window default configuration
set -g @catppuccin_window_default_fill "number"

Without this PR it will look like this:

[mklbravo]

Thanks for the approval @vvorobev !

[mklbravo]

Thank you @vdbe !