Install project with bazel using a local_repository

[coltonmorris]

I'd like to start pulling in the package similar to how rules_typescript does - which is by including all of the pertinent bazel files in the npm package, and then in your workspace using a local_repository. Not only will this make installing easier by following a convention, but it also cleans up some dependency version snafus.

Some changes to achieve this:

• Include the defs.bzl file in the npm package (I could use some direction on this one).
• Build the protoc plugin binary within bazel differently. It currently relies on the src directory which isn't part of the npm package. Can investigate just pulling in the binary, or building using the lib directory.
• Update readme.
• Test to compare bazel's binary with the non-bazel one.

[coltonmorris]

#129

Shy'd away from using the local_repository, and cleaned up the installation instead.

[stale]

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