Update docs

docs/changelog

@@ -41,6 +41,7 @@
 - clang-format can now be applied to the whole code tree without breaking compilation.
 - Added more check options to .clang-tidy file.
 - Default Python version is now >= 3.4. Python 2.7 still can be used in systems where Python 3 is not available (e.g., CentOS 7, Debian 8, Ubuntu 10.04).
+- CMake now passes the CMAKE_BUILD_TYPE (or configuration in multi-configuration generators like Xcode) to modules built along gnss-sdr (e.g, the volk_gnsssdr library and googletest). Build types available: None, Release (by default), Debug, RelWithDebInfo, MinSizeRel, Coverage, NoOptWithASM, O2WithASM, O3WithASM, ASAN.
 
 
 ### Improvements in Portability:
@@ -51,6 +52,7 @@
 - Added toolchain files for building gnss-sdr and the volk_gnsssdr library in several ARM processor architectures, including those in Raspberry Pi 3 and 4.
 - The software can now be built using Xcode (passing -GXcode to CMake) without previous manual installation of volk_gnsssdr.
 - Now the volk_gnsssdr library can be built on Microsoft Windows.
+- Improved CMake script for cross-compilation and for the detection of AVX, AVX2 and NEON (v7 and v8) instructions.
 
 
 ### Improvements in Reliability:
@@ -67,6 +69,7 @@
 ### Improvements in Testability:
 
 - Add receiver runtime to position_test report.
+- Improvements in FPGA unit tests.
 
 
 ### Improvements in Usability:
@@ -77,6 +80,7 @@
 - Added a Python 3 plotting script to show relative performance of generic volk_gnsssdr kernels wrt SIMD fastest versions.
 - Added reporting of velocity in the terminal.
 - Added reporting of user clock drift estimation, in ppm, in the Pvt_Monitor and in internal logging (debug mode).
+- Updated documentation generated by Doxygen, now the pdfmanual target works when using ninja.