[SeaBIOS] Patch: Add multiboot-capability to documentation

[Dennis Guse]

Hello,

so far the multiboot support is not included in the documentation.
This small patch changes docs/Runtime_config.md to include multiboot.

I think adding how to use multiboot with Grub would be nice, but this
does not seem to fit to the content of Runtime_config.md.
Do you have any suggestions where to put it?

>
This example shows how to start SeaBIOS from Grub2 via multiboot.
SeaVGABIOS is passed as a module.

```
set root=(usb0,msdos1)
multiboot /bios.elf.bin
module /vgabios.bin name=vgaroms/seavgabios.bin
boot
```
>

Best,
---
Dennis Guse
-------------- next part --------------
diff --git a/docs/Runtime_config.md b/docs/Runtime_config.md
index 5171296..af737ec 100644
--- a/docs/Runtime_config.md
+++ b/docs/Runtime_config.md
@@ -1,7 +1,10 @@
-SeaBIOS can read several configuration items at runtime. On coreboot
-the configuration comes from files located in CBFS. When SeaBIOS runs
-natively on QEMU the files are passed from QEMU via the fw_cfg
-interface.
+SeaBIOS can read several configuration items at runtime:
+
+* on coreboot via CBFS,
+* on QEMU via fw_cfg, or
+* on multiboot bootloader (eg, Grub2) as modules.
+
+Basically, all three present different read-only file systems.
 
 This page documents the user visible configuration and control
 features that SeaBIOS supports.