Added Dockerfile for build

[nrawling]

Pretty straightforward Dockerfile. I picked Debian because it is pretty lightweight compared to other distros, but not prone to libc challenges like Alpine. I managed most dependencies except icu-config, which now appears to be deprecated.

A multi-stage build that does user configuration, etc. is certainly possible. However, I don't know if it is worthwhile to remove the build infrastructure, which isn't terribly large as it is. I think a lot could be done with using environment variables to configure external state for DB, etc.

It is failing two tests:

Running tests for json:
TEST FAILURE: json.string.5
command: think json(string, accent(foo, f:o))
result: "foo"
pattern: ^"f\u00F6o"

TEST FAILURE: json.string.6
command: think json_query(json(string,accent(foo,f:o)), unescape)
result: foo
pattern: ^f\xF6o

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81 tests, 79 succeeded, 2 failed (0 expected failures)
failed tests:
json.string.5, json.string.6

[nrawling]

This PR begins work on #1304