Add amdvlk as an option for Vulkan (#2)

- Add `--vk=amdvlk` to startgame;
- Update README.md to include `--vk=amdvlk` option.

README.md

@@ -61,6 +61,9 @@ startgame ${options} -- %command%
 - `--vk=amdpro`
   Forces VK ICD to amdpro (for AMD GPU's only)
 
+- `--vk=amdvlk`
+  Forces VK ICD to amdvlk (for AMD GPU's only)
+
 - `--vk=radeon`
   Forces VK ICD to radeon (for AMD GPU's only)
 
@@ -79,6 +82,8 @@ startgame ${options} -- %command%
 
 - `vulkan-amdgpu-pro`, `lib32-vulkan-amdgpu-pro` (optional)
 
+- `amdvlk`, `lib32-amdvlk` (optional)
+
 - `gamescope` (optional)
 
 - `sdl2`, `lib32-sdl2` (optional)

startgame

@@ -23,6 +23,7 @@ if [[ $# -eq 0 ]] || [[ "${1:-}" == '--help' ]]; then
     --soldier         Enable Steam Soldier (see #notes)
     --term            Opens a terminal instead of the game (exposes game command in "\$GAME_CMD")
     --vk=amdpro       Forces VK ICD to amdpro (for AMD GPU's only)
+    --vk=amdvlk       Forces VK ICD to amdvlk (for AMD GPU's only)
     --vk=radeon       Forces VK ICD to radeon (for AMD GPU's only)
     --wayland         Don't force XWayland
 
@@ -32,6 +33,7 @@ if [[ $# -eq 0 ]] || [[ "${1:-}" == '--help' ]]; then
     * mangohud, lib32-mangohud
     * obs-vkcapture
     * vulkan-amdgpu-pro, lib32-vulkan-amdgpu-pro (optional)
+    * amdvlk, lib32-amdvlk (optional)
     * gamescope (optional)
     * sdl2, lib32-sdl2 (optional)
     * Wine with FSR pattches (optional)
@@ -106,6 +108,10 @@ function prepare() {
       _DRIVER='amdpro'
       shift 1
       ;;
+    '--vk=amdvlk')
+      _DRIVER='amdvlk'
+      shift 1
+      ;;
     '--vk=radeon')
       _DRIVER='radeon'
       shift 1
@@ -207,6 +213,8 @@ function prepare() {
   # * Apply features
   if [[ "$_DRIVER" == 'radeon' ]]; then
     GAMEMODERUNEXEC+=" VK_ICD_FILENAMES=${_ICD_PATH}/radeon_icd.i686.json:${_ICD_PATH}/radeon_icd.x86_64.json"
+  elif [[ "$_DRIVER" == 'amdvlk' ]]; then
+    GAMEMODERUNEXEC+=" VK_ICD_FILENAMES=${_ICD_PATH}/amd_icd32.json:${_ICD_PATH}/amd_icd64.json"
   elif [[ "$_DRIVER" == 'amdpro' ]]; then
     GAMEMODERUNEXEC+=" VK_ICD_FILENAMES=${_ICD_PATH}/amd_pro_icd32.json:${_ICD_PATH}/amd_pro_icd64.json"
   fi