text annotation levels added working with heatmap. Another axis improvements

[gilbertogalvis]

This PR improve greatly the work with heatmap function. With this the text annotations levels were added to the plots. It works very well for examples in https://github.com/plotly/ssim_baselines/tree/main/matlab/code-examples/data-distribution-plots/heatmap

Example of usage:

load patients
tbl = table(LastName,Age,Gender,SelfAssessedHealthStatus,...
    Smoker,Weight,Location);
h = heatmap(tbl,'Smoker','SelfAssessedHealthStatus');

mf = gcf;
f = fig2plotly(mf, 'offline', 0); 

Attach result examples bellow

link to chart-studio

https://chart-studio.plotly.com/~galvisgilberto/3832/#/
https://chart-studio.plotly.com/~galvisgilberto/3836/#/
https://chart-studio.plotly.com/~galvisgilberto/3840/#/
https://chart-studio.plotly.com/~galvisgilberto/3842/#/
https://chart-studio.plotly.com/~galvisgilberto/3844/#/
https://chart-studio.plotly.com/~galvisgilberto/3846/#/
https://chart-studio.plotly.com/~galvisgilberto/3848/#/
https://chart-studio.plotly.com/~galvisgilberto/3850/#/