Add CMake install targets and package discovery

[j0057]

Fixes some warnings about missing minimum CMake version and project statements.
Also simplifies the CMakeLists.txt by using file globbing for the COMPONENT_SRCS
variable instead of naming each file individually.

Adds targets for installing header files to <prefix>/include and the static
library to <prefix>/lib.

Finally, adds a file to make CMake package discovery work, so that after having
built and installed u8g2, a CMake-based project can use u8g2 by using the
find_package CMake command.

References:

• https://cmake.org/cmake/help/book/mastering-cmake/chapter/Install.html
• https://cmake.org/cmake/help/book/mastering-cmake/chapter/Finding%20Packages.html
• https://cmake.org/cmake/help/latest/command/find_package.html
• https://cmake.org/cmake/help/book/mastering-cmake/cmake/Help/guide/importing-exporting/index.html#exporting-targets