Rich text formatting commands

There are a few different rich text formatting commands scattered around the place.

For example, our Slack support defines several of its own formatting commands:

https://github.com/knausj85/knausj_talon/blob/000015ed1bd4cb1109d7d6ddaaa4146821821d70/apps/slack/slack_mac.talon#L31-L39

If we search for justify, we can find some Figma and PowerPoint .talon files that, among other things, define commands for text alignment and common text styles.

https://github.com/knausj85/knausj_talon/blob/273b7c9a62de6c12fe9baae175843eb6f0caab2b/apps/platforms/mac/powerpoint/powerpoint.talon#L15-L22

https://github.com/knausj85/knausj_talon/blob/f44077d19aafb8aca35be6d152c73a1252dfb837/apps/figma/figma.talon#L41-L56

(above are in forks, links edited to unfurl)

Searching for strike nets us the rest of the Microsoft Office suite, Evernote, and some Markdown and org-mode. Searching for bold and italic also finds some LaTeX support.

We should probably come up with a consistent grammar for basic rich text formatting. We probably want at least:

• bold
• italics
• underline
• strikethrough (#528)
• text alignment (left, centre, right, justify)
• font size (up/down)?
• lists (bullet and number)

[rntz]

See previously #159

[lab-do]

I think we need a rich text formatting tag for it, something like this:

tag: user.rich_text
-

text left: user.text_align_left() 
text right: user.text_align_right() 
text center: user.text_align_center() 
text justify: user.text_align_justify()

text bold: user.text_font_bold()
text italic: user.text_font_italic()
text underline: user.text_font_underline()
text strikethrough: user.text_font_strikethrough()

text (big | bigger): user.text_font_size_up()
text (small | smaller): user.text_font_size_down()
text thicker: user.text_font_weight_up() 
text thinner: user.text_font_weight_down() 

text high: user.text_line_height_up()
text low: user.text_line_height_down()