Typography classes & styles

[jvine]

Below are the font sizes, weights, and letter-spacing for the classes defined here:
https://material.io/develop/web/components/typography/

(Specify rems; px are for reference.)

class	rem	px	weight	line-height	letter-spacing	other
Headline 1	2.822rem	45.159	300	1.2em	-.015em
Headline 2	1.575rem	25.192	300	1.33em	0
Headline 3	1.383rem	22.127	300	1.33em	0
Headline 4	1.215rem	19.436	400	1.45em	0.007em
Headline 5	1.138rem	18.215	400	1.55em	0.005em
Headline 6	1.067rem	17.072	400	1.6em	0.01em
Subtitle 1	0.937rem	14.995	300	1.6em	.015em
Subtitle 2	0.878rem	14.053	500	1.75em	.02em
Body 1	1rem	16px	400	1.6em	0
Body 2	0.878rem	14.053	400	1.6em	.015em
BUTTON	0.878rem	14.053	500	2.25rem	0.09em	uppercase
Caption	0.772rem	12.344	400	1.6rem	0.033em
OVERLINE	0.678rem	10.842	500	2em	.166em	uppercase

assign classes

Some specific class assignments are needed to override default sizes.

element	assign class
window title <h2>	Heading 6
companion window <h3>	Subtitle 1
<dt>	Subtitle 2
<dd>	Body 1
"Current item" etc. labels in About panel	OVERLINE
window dialog <h3>	Heading 2 (we don't have any of these yet)