* Update release number to 106.

Public Issues:

  * Add searchbox and generate search index for the chunked HTML target.
    Note that doing this requires several new toolchain components to build
    the `chunked` target (public issue 578 / internal issue 1352).
  * Remove descriptions of flink:vkCreateSampler sampler constraints which
    were repeated in the valid usage statements (public pull request 648).
  * Fix sense of conditional around a valid usage statement in the
    <<copies>> chapter (public issue 942).

Internal Issues:

  * Add missing pname:extent.width and pname:extent.height valid usage
    statements for flink:vkCmdClearAttachments (internal issue 1583).
  * Fix some inconsistencies in structures and corresponding pname:sType
    enumerant names by renaming
    sname:VkPhysicalDeviceShaderDrawParameterFeatures ->
    slink:slink:VkPhysicalDeviceShaderDrawParametersFeatures;
    sname:VkPhysicalDeviceVariablePointerFeatures ->
    slink:VkPhysicalDeviceVariablePointerFeatures;
    sname:VkPhysicalDeviceVariablePointerFeaturesKHR ->
    slink:VkPhysicalDeviceVariablePointerFeaturesKHR;
    sname:VkPhysicalDeviceBufferAddressFeaturesEXT ->
    slink:VkPhysicalDeviceBufferDeviceAddressFeaturesEXT;
    etext:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SHADER_DRAW_PARAMETER_FEATURES
    ->
    ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SHADER_DRAW_PARAMETERS_FEATURES;
    etext:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VARIABLE_POINTER_FEATURES ->
    ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VARIABLE_POINTERS_FEATURES;
    etext:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VARIABLE_POINTER_FEATURES_KHR ->
    ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_VARIABLE_POINTERS_FEATURES_KHR;
    and etext:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_BUFFER_ADDRESS_FEATURES_EXT
    ->
    ename:VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_BUFFER_DEVICE_ADDRESS_FEATURES_EXT.
    The old names are still available as aliases for backwards
    compatibility. This change required introducing valid XML markup which
    externally written XML processing scripts may need to be modified to
    accomodate, to support multiple aliases of a single command or token
    name (internal issue 1592).
  * Add slink:VkDevice as the first parameter to flink:vkSetLocalDimmingAMD
    (internal issue 1618).
  * Improve CI header compilation tests to test all Vulkan platform
    includes, using fake platform headers where needed, and change the
    `allchecks` Makefile target to use the more comprehensive
    `check_spec_links.py` script instead of the retired `checkinc` and
    `checklinks` targets.
  * Move descriptions of the ASTC compressed texture decode mode from the
    <<appendix-compressedtex-astc,appendix>> to the recently updated
    external Khronos Data Format Specification.
  * Fix minor markup and spelling issues in the `VK_NV_ray_tracing`
    extension.