Signet desktop client version 0.9.18 release notes

### New features

- 32-bit Linux builds now available, and SSE4 CPU extensions are not required
- Added a man page
- Added an icon to the signet.desktop file
- Added a "make install" target on Linux (installs executable, udev rule, man
  page, launcher shortcut with the signet icon)
- Source tarball generation via CI/CD
- 32- and 64-bit Linux executables built by CI/CD

### Enhancements

- Updated documentation and converted into a README
- Updated URLs for downloads, as Adam at Hax0rbana picked up maintence of all
  codebases and is now hosting the documentation and downloads
- Changed location of executable to be /usr/bin instead of /usr/local/bin to
  be more standards compliant
- Pulled in typo fix from keepassx submodule
- Pulled in updated config.guess from signet-core submodule

### Bug fixes

- Fixed compilation error due to variable redefinition
