Update README.md to add a heading to documentation section

README.md

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 Templates parameters are the element data type of the vectors and the vector width in bytes (e.g. 16 for SSE* and NEON, 32 for AVX/AVX2). This makes it possible to flexibly change the data type and the vector instruction set for entire portions of the code. Moreover, many implementation details at the intrinsics level are hidden by **T-SIMD**. SSE*, AVX/AVX2, AVX-512, and ARM NEON vector instruction sets are currently supported. In addition, higher-level functions like transposition are provided.
 
+## Documentation
+
 The documentation of **T-SIMD** is available [here](https://ti-uni-bielefeld.github.io/T-SIMD/).
 
 For documentation of functions and classes, see the [Library Reference](topics.html).