lwtnn/lwtnn: Version 2.12

This release fixes a number of bugs: Properly handle InputLayer in Keras Sequential models (thanks @QuantumDancer) Fix bug supporting TimeDistributed BatchNormalization layers Fix bugs in lwtnn-split-keras-network.py Fix some annoying warnings in compilation Fixes for compilation errors in gcc11 (thanks @matthewfeickert) Replace broken link for boost in the minimal install (now getting boost from a public CERN URL) There were some tweaks to reduce element-wise calls through std::function in activation functions. This should mean a lot less pointer dereferencing. There were also some improvements to overall code health, all from @matthewfeickert: Add Github Actions based CI Code linting, also add pre-commit hooks to run linting, and enforce some of this in CI Expand text matrix to include C++17, C++20, and gcc11 Specify dependency versions more carefully, increase the range of allowed CMake version