[SYCL][DOC] Added table with DPC++ extensions status

Signed-off-by: Vlad Romanov <vlad.romanov@intel.com>

Author: romanovvlad

sycl/doc/extensions/README.md

@@ -1,3 +1,34 @@
 # Extensions
 
-This is where documents can be found that propose extensions to the SYCL specification.
+The directory contains documents that describe DPC++ extensions to SYCL
+specification.
+
+DPC++ extensions status:
+
+|  Extension  |    Status   |   Comment   |
+|-------------|:------------|:------------|
+| [SYCL_INTEL_bitcast](Bitcast/SYCL_INTEL_bitcast.asciidoc) | Proposal | |
+| [C and C++ Standard libraries support](C-CXX-StandardLibrary/C-CXX-StandardLibrary.rst) | Partially supported | |
+| [SYCL_INTEL_data_flow_pipes](DataFlowPipes/data_flow_pipes.asciidoc) | Supported | |
+| [SYCL_INTEL_deduction_guides](deduction_guides/SYCL_INTEL_deduction_guides.asciidoc) | Supported | |
+| [SYCL_INTEL_device_specific_kernel_queries](DeviceSpecificKernelQueries/SYCL_INTEL_device_specific_kernel_queries.asciidoc) | Proposal | |
+| [SYCL_INTEL_enqueue_barrier](EnqueueBarrier/enqueue_barrier.asciidoc) | Proposal | |
+| [SYCL_INTEL_extended_atomics](ExtendedAtomics/SYCL_INTEL_extended_atomics.asciidoc) | Proposal | |
+| [SYCL_INTEL_group_algorithms](GroupAlgorithms/SYCL_INTEL_group_algorithms.asciidoc) | Proposal | |
+| [SYCL_INTEL_group_mask](./GroupMask/SYCL_INTEL_group_mask.asciidoc) | Proposal | |
+| [FPGA selector](IntelFPGA/FPGASelector.md) | Supported | |
+| [FPGA reg](IntelFPGA/FPGAReg.md) | Supported | |
+| [SYCL_INTEL_kernel_restrict_all](KernelRestrictAll/SYCL_INTEL_kernel_restrict_all.asciidoc) | Supported | |
+| [SYCL_INTEL_attribute_style](KernelRHSAttributes/SYCL_INTEL_attribute_style.asciidoc) | Proposal | |
+| [Queue Order Properties](OrderedQueue/OrderedQueue_v2.adoc) | Supported | |
+| [Queue Shortcuts](QueueShortcuts/QueueShortcuts.adoc) | Supported | |
+| [Reductions for ND-Range Parallelism](Reduction/Reduction.md) | Partially supported | |
+| [SYCL_INTEL_relax_standard_layout](RelaxStdLayout/SYCL_INTEL_relax_standard_layout.asciidoc) | Supported | |
+| [SYCL_INTEL_reqd_work_group_size](ReqdWorkGroupSize/SYCL_INTEL_reqd_work_group_size.asciidoc) | Supported | |
+| [SPV_INTEL_function_pointers](SPIRV/SPV_INTEL_function_pointers.asciidoc) | Supported | |
+| [SPV_INTEL_inline_assembly](SPIRV/SPV_INTEL_inline_assembly.asciidoc) | Supported | |
+| [SYCL_INTEL_static_local_memory_query](StaticLocalMemoryQuery/SYCL_INTEL_static_local_memory_query.asciidoc) | Proposal | |
+| [SYCL_INTEL_sub_group_algorithms](SubGroupAlgorithms/SYCL_INTEL_sub_group_algorithms.asciidoc) | Proposal | |
+| [Sub-groups for NDRange Parallelism](SubGroupNDRange/SubGroupNDRange.md) | Proposal | |
+| [SYCL_INTEL_unnamed_kernel_lambda](UnnamedKernelLambda/SYCL_INTEL_unnamed_kernel_lambda.asciidoc) | Supported | |
+| [Unified Shared Memory](USM/USM.adoc) | Supported | |