Bug fixes and test case resturcture for export to vega functions

[Delen0828]

Updates:

• Added documentation in vega_export_docs.html and vega_export_docs.js
• Restructured the test script from one file to individual files in test/scripts
• Updated .gitignore to ignore coverage and test reports.
• Modify gramm/@gramm/draw.m: clean up facet handling, make point border defaults robust, remove interactive toolbar/interaction settings, and enforce a white figure background.
• Extend gramm/@gramm/export_vega.m with numerous helpers: MATLAB->Vega color conversion, point style extraction (border color/width), categorical palette selection, group counting, graphics-handle utilities, sanitizers, and extraction routines for stat_fit, stat_ellipse and bins. Update chart layer builders to honor point border styles, use the new categorical color range, and adjust grouped bar nesting/marks and tooltips.

Documentation is available at gramm/vega_export_docs.html.

Test cases are validated by ExamplesDrivenTester by running gramm/test.m

[piermorel]

Hi @Delen0828 ,

Thanks for the pull request. I see that some changes in draw.m are regressions (removal of dark mode handling, of 3D plot interaction settings), while others are improvements. Could you indicate the cause for regressions (note that dark theme handling was improved in the master branch in commit 48b1783, maybe bring over the changes if dark mode caused problems for you ?) and propose quick minimal examples (in this discussion) to showcase improvements ?

About the handling of examples and the use of ExamplesDrivenTester, this was recently overhauled by @slahoti1 from Mathworks on the master branch (ca51fd4 and 1b9f667) and I see that you handled things differently, could you model your structure off of his ? Or rebase the branch off the master so that a merge down the line can be easier ?

[Delen0828]

Hi Pierre, thanks for your feedback! I believe some of the issues you mention in draw.m is because I started with an earlier version of gramm and didn't keep up with the latest versions. I will look into them and try sync with the latest commits.

For the ExamplesDrivenTester, the examples are really helpful and I will try to follow them.