Add font name, license and pyglet tips to the text guide

[pvcraven]

Summary

Closes #1171 with a small addition to the text guide's "Fonts that come with your game" section. The change is 8 lines in doc/programming_guide/text.rst.

• Font names: some font viewers add the style to the name, such as "Grand Hotel, Regular" for "Grand Hotel". If you're not sure of the name, use the file's path as font_name, which works since Load font files passed as font_name, and accept lists of names #2922.
• Licenses: many free fonts, such as most on Google Fonts, use the SIL Open Font License, which lets you ship them with your game. Include the font's license file.
• More detail: a link to pyglet's text guide, as einarf suggested in the issue.

Most of what #1171 asked for in 2022 is covered by other changes since then:

• The guide shows how to use your own TTF files.
• A file path works as font_name, so you don't need to know the font's name.
• Since Make the bundled Liberation Sans the default font #2957, the default font comes with Arcade.

This covers what was left without a new tutorial.

The docs build adds no warnings, and both links render.

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