README: add abi-compliance-checker into install instructions

9 jobs for master
Status Job ID Name Coverage
  Test
passed #1050777
nettle3
Build and Check - clang

00:17:52

passed #1050774
x86 nettle3
Build and Check - separate build dir (x86)

00:22:01

passed #1050779
nettle3 wine mingw
Build and Check for windows in separate build dir

00:17:53

passed #1050778
nettle3
Build and Check in FIPS140-2 mode

00:23:44

passed #1050773
ubsan nettle3
Build and Check with C99 and ubsan

00:21:39

passed #1050772
nettle3
Build and Check with asan

00:19:11

passed #1050780
nettle3
Build and Check with valgrind

00:17:15

passed #1050775
x86-64 nettle3 abi-checker
Build with ABI-check (x86-64)

00:08:03

passed #1050771
nettle3
Compile minimal library

00:07:31