Crystal 1.8.0+ require pcre2.
Let's also add `RUN ameba -v` to check if the binary actually works.
Fixes cases like this:
```shell
$ docker run --rm -ti ameba:latest sh
Error loading shared library libpcre2-8.so.0: No such file or directory (needed by /usr/bin/ameba)
Error relocating /usr/bin/ameba: pcre2_get_ovector_count_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_config_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_get_ovector_pointer_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_match_data_create_from_pattern_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_jit_stack_assign_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_code_free_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_match_context_create_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_jit_compile_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_compile_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_get_error_message_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_jit_stack_create_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_match_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_match_data_free_8: symbol not found
Error relocating /usr/bin/ameba: pcre2_pattern_info_8: symbol not found
```
