Gersemi

Fixed
- Fix "unknown command" regression. (52)

Fixed
- Proper formatting of first `<artifact-option>...` group in `INSTALL(TARGETS)` command. (51)

Added
- Add support for extensions and provide example extension as a template.

Fixed
- Recognize `unquoted_legacy` rule of CMake language. (49)
- Cut down excessive memory usage when used on a project with big number of files.
- Correctly recognize keywords from download, upload and patch steps of `ExternalProject_Add` in `FetchContent_Declare`. (50)

Fixed
- fix `--no-quiet` (43)

Added
- Add `disable_formatting`. (35)
- `--config` can be used to provide explicit path to configuration file. (35)
- Add `--print-config` to print outcome configuration in one of three variants: minimal, verbose, default. (35)
- Warn about options not supported through configuration file.

Changed
- Configuration has been split into two kinds: outcome and control. Outcome configuration can be changed through either configuration file or command line arguments whereas control configuration be changed only through command line.
- Search strategy for `.gersemirc` file has been changed so that the file closest to given source file is picked instead of using `.gersemirc` that it the most commont among files passed to gersemi.
- `--default-config` is removed because its functionality is subsumed by `--print-config default`.
- `cache`, `color`, `quiet` and `workers` can be changed only through command line.

Fixed
- custom command definitions nested inside other definitions are picked as well (39)
- colors stripping when output is redirected (40)

Fixed
- support missing keywords in `file(MAKE_DIRECTORY)` (38)
- support missing keywords in `try_compile`
- add support for experimental `install(PACKAGE_INFO)`