Out-of-the-box support for projects using the GNU toolset

At least from the webpage this blueprint is currently highly clang/cmake centric. This FR is about extending that.

### Feature Description:

* example project
* task definitions (possibly "configure" as a step that is executed once; "build" which executes "make", likely placing `-g` (or even `-ggdb3` to CFLAGS/CXXFLAGS)
* clangd integration (that likely would mean to wrap the `make` invocation into `bear` to provide the necessary clangd configuration)
* possibly pre-configured/installed extensions for Makefiles and autoconf/automake (I can recommend `maelvalais.autoconf` for both).