feat: add remaining architectures

Recent design improvements permit building all of Zephyr's supported architectures simultaneously.  So why not?

PR: zmkfirmware/zmk-docker#58

README.md

@@ -2,8 +2,24 @@ Lightweight Docker images for [ZMK][zmk].
 
 ### Platforms
 
+#### Tested
 - `arm`
 
+#### Not Tested
+- `arc`
+- `arm64`
+- `nios2`
+- `riscv64`
+- `sparc`
+- `x86_64`
+- `xtensa_intel_apl_adsp`
+- `xtensa_intel_bdw_adsp`
+- `xtensa_intel_byt_adsp`
+- `xtensa_intel_s1000`
+- `xtensa_nxp_imx8m_adsp`
+- `xtensa_nxp_imx_adsp`
+- `xtensa_sample_controller`
+
 ### Images
 
 #### build

architectures.yml

@@ -1 +1,14 @@
+- arc
 - arm
+- arm64
+- nios2
+- riscv64
+- sparc
+- x86_64
+- xtensa_intel_apl_adsp
+- xtensa_intel_bdw_adsp
+- xtensa_intel_byt_adsp
+- xtensa_intel_s1000
+- xtensa_nxp_imx8m_adsp
+- xtensa_nxp_imx_adsp
+- xtensa_sample_controller