bug/7471: fix gantt font size and auto scale the barHeight and allow gantt to take themeVariables#7537

ankithapai wants to merge 5 commits intomermaid-js:developmermaid-js/mermaid:developfrom

ankithapai:bug/7471_gnatt-chart-theme-variables-font-sizeankithapai/mermaid:bug/7471_gnatt-chart-theme-variables-font-sizeCopy head branch name to clipboard