message: Update first sentence in README
  Related PR:
diff: [![DOI](https://joss.theoj.org/papers/10.21105/joss.02260/status.svg)](https://doi.org/10.21105/joss.02260)
  Ginkgo is a high-performance linear algebra library for manycore systems, with a
  -focus on sparse solution of linear systems. It is implemented using modern C++
  -(you will need at least C++14 compliant compiler to build it), with GPU kernels
  -implemented in CUDA and HIP.
  +focus on the solution of sparse linear systems. It is implemented using modern C++
  +(you will need an at least C++14 compliant compiler to build it), with GPU kernels
  +implemented in CUDA, HIP, and DPC++.
  Performance
  