daniel/theme-setting (#87)

- Themes can be loaded from disk and built-in
- Themes can be selected in a new themes menu of the settings screen
- Some touch-ups to existing themes
- The saved theme is persisted in nvs

Reviewed-on: https://codeberg.org/cool-tech-zone/tangara-fw/pulls/87
Reviewed-by: cooljqln <cooljqln@noreply.codeberg.org>
Co-authored-by: ailurux <ailuruxx@gmail.com>
Co-committed-by: ailurux <ailuruxx@gmail.com>

luals-stubs/theme.lua

@@ -0,0 +1,28 @@
+--- @meta
+
+--- @class theme
+local theme = {}
+
+--- Loads a theme from a filename, this can be either builtin (ie, located in
+--- "/lua/") or on the sdcard (in, '/sdcard/.themes/')
+--- If successful, the filename will be saved to non-volatile storage.
+--- Returns whether the theme was successfully loaded 
+--- @param filename string
+--- @return boolean
+function theme.load_theme(filename) end
+
+--- Sets a theme directly from a table. Does not persist between restarts. 
+--- @param theme
+function theme.set(theme) end
+
+--- Set the style name (similar in concept to a css selector) for an object
+--- This will set any styles associated with that style name on the object
+--- @param obj Object The object to set a particular style on
+--- @param style string The name of the style to apply to this object
+function theme.set_style(obj, style) end
+
+--- Returns the filename of the saved theme
+--- @return string 
+function theme.theme_filename() end
+
+return theme