Support custom font sizes

[michael-yx-wu]

Add support for custom label font size in the following places:

• Bar
• StackedBar
• Scatter
• Axes (Category, Numeric, Time)

cc @Nifdee @billytrend

Testing

SVG measures distance to text elements using the text baseline instead of the top-left corner like it does with most other elements. I've taken care to redraw or reset the typesettable measurer's cache where applicable to make subsequent renders draw the text in the right place. When playing with the quicktests, please double check that the label is positioned reasonably as font size changes i.e. it doesn't crowd out other elements, it's hidden when there is no space to draw, etc.

⚠️ The blueprint-bot's quicktest link is broken, so I recommend testing by checking out the repo and running yarn start and navigate to the links below. Gifs show what you should expect to see. I recommend using node 8.10.0 with this repo, just to be consistent with the CI environment.

Bar

http://localhost:9999/quicktests/dev/index.html#functional/bar_plot_label_font_size

Scatter

http://localhost:9999/quicktests/dev/index.html#functional/scatter_plot_label_font_size
Something weird is happening w/ the scatter plot labels. Unclear why the size "stutters" when increasing font size. Note that internally, we do not use scatter plot labels.

Category axis

http://localhost:9999/quicktests/dev/index.html#functional/category_axis_label_font_size

Numeric axis

http://localhost:9999/quicktests/dev/index.html#functional/numeric_axis_label_font_size

Time axis

http://localhost:9999/quicktests/dev/index.html#functional/time_axis_label_font_size

[blueprint-bot]

Clean up jsdoc

Demo: quicktests | fiddle

[Nifdee]

Tested locally, seems to work fine.

[blueprint-bot]

Address nits

Demo: quicktests | fiddle