fw-rust: Break everything down in multiple files

To reduce length of `main.rs` and therefor improve readability create
source files for:

- Assets (`assets.rs`): Contains all graphical assets such as the
  splash screen assets, symbols and the symbol table.
- LCD (`lcd.rs`): Contains all lower level things regarding the LCD
  such as the `Lcd` struct and its implementations.
- Screen (`screen/mod.rs`):
    - Splash (`screen/splash.rs`)
    - Home (`screen/home.rs`)
    - Setup (`screen/setup.rs`)

In the future it would probably make sense to move the LCD module into
the screen module.

firmware/rust/src/screen/splash.rs

@@ -0,0 +1,48 @@
+use super::Screen;
+use crate::{
+    assets::{ONDERS_ORG, SACRED_CHAO},
+    lcd::Lcd,
+};
+use atmega_hal::{clock::MHz8, delay::Delay};
+use embedded_hal::{blocking::delay::DelayMs, spi::FullDuplex};
+use nb::block;
+
+pub struct Splash;
+
+impl Screen for Splash {
+    fn draw(&self, lcd: &mut Lcd) {
+        let mut delay = Delay::<MHz8>::new();
+
+        for (i, page) in SACRED_CHAO.iter().enumerate() {
+            lcd.move_cursor(31, 1 + i as u8);
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            lcd.cd.set_high();
+
+            for segment in page {
+                block!(lcd.spi.send(*segment)).unwrap();
+            }
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            lcd.cd.set_low();
+        }
+
+        for (i, page) in ONDERS_ORG.iter().enumerate() {
+            lcd.move_cursor(27, 6 + i as u8);
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            lcd.cd.set_high();
+
+            for segment in page {
+                block!(lcd.spi.send(*segment)).unwrap();
+            }
+
+            // TODO: This delay fixes issues, try find a better solution
+            delay.delay_ms(1_u8);
+            lcd.cd.set_low();
+        }
+    }
+}