README: some text; let's see what this looks like

README.md

@@ -1,3 +1,70 @@
 # F00bar
 
 [![pipeline status](https://gitlab.com/dnkl/f00bar/badges/master/pipeline.svg)](https://gitlab.com/dnkl/f00bar/commits/master)
+
+![screenshot](screenshot.png "Example configuration")
+
+
+## Index
+
+1. [Configuration](#configuration)
+
+
+## Configuration
+
+### Overview
+
+F00bar is configured using YAML, in `~/.config/f00bar/config.yml`. It
+must define a top-level dictionary named **bar**:
+
+    bar:
+      height: 26
+      location: top
+      background: 000000ff
+
+
+
+### Types
+
+There are a couple types used that are specific to f00bar.
+
+- **font**: this is a string in _fontconfig_ format. Example of valid values:
+  + Font Awesome 5 Brands
+  + Font Awesome 5 Free:style=solid
+  + Dina:pixelsize=10:slant=italic
+  + Dina:pixelsize=10:weight=bold
+- **color**: an rgba hexstring; RRGGBBAA. Examples:
+  + ffffffff: white, no transparancy
+  + 000000ff: black, no transparancy
+  + 00ff00ff: green, no transparancy
+  + ff000099: red, semi-transparent
+
+
+### Bar
+
+- `height` (_int_, **required**): the height of the bar, in
+  pixels. Note that the bar will _always_ occupy the entire width of
+  the monitor.
+- `location` (_enum_, **required**): one of `top` or `bottom`. Should
+  be self-explanatory.
+- `background` (_color_, **required**): background color, in
+  _rgba_. Thus, in the example above, the background is set to _black_
+- `left-spacing` (_int_): space, in pixels, added **before** each module
+- `right-spacing` (_int_): space, in pixels, added **after** each module
+- `spacing` (_int_): short-hand for setting both `left-spacing` and
+  `right-spacing`
+- `left-margin` (_int_): left-side margin, in pixels
+- `right-margin` (_int_): right-side margin, in pixels
+- `margin` (_int_): short-hand for setting both `left-margin` and
+  `right-margin`
+- `border` (_dictionary_): configures a border around the status bar
+- `font` (_font_): default font to use
+- `foreground` (_color_): default foreground (text) color to use
+- `left` (_list_): left-aligned modules
+- `center` (_list_): center-aligned modules
+- `right` (_list_): right-aligned modules
+
+The `border` dictionary has the following attributes:
+
+- `width` (_int_, **required**): with, in pixels, of the border
+- `color` (_color_, **required**): the color of the border