feat: Add tilemaker to PATH

[langbein-daniel]

By creating a symlink from /tilemaker to /usr/bin/tilemaker, one can execute the tilemaker command e.g. from within a shell.

This makes it possible to use the built tilemaker binary as if it was "installed". If one does a Docker multistep build that uses the tilemaker Docker image, one can then simly use RUN tilemaker ... and does not need to know where the binary is actually stored.

[daniel-j-h]

I revamped our dockerfile in https://github.com/systemed/tilemaker/pull/713 and added the tilemaker binaries to PATH in there, too. Let me know if this resolves your issue and if we can close this pull request as solved.