docs: README stub (#2)

* docs: README stub

* docs: more readme

README.md

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 # doggo
-Inspecting big Datadog traces in the CLI
+🐕🔎 Inspecting big Datadog traces in the CLI
+
+## Why?
+
+The Datadog trace-viewing UI performance greatly degrades as the number of spans in a single trace increases and within
+a trace, it is often painful to find the span you are interested in as there is no way to "jump" to a span directly.
+
+This is an attempt at solving that problem: using `doggo`, you can inspect large trace json blobs and get to the subtree
+corresponding to spans of interest in a few keystrokes without having to worry about your browser running out of memory.
+At present, you will have to have the json you want to inspect handy -- the tool simply makes it more palatable.
+
+## Usage
+
+To get `doggo` on your machine, you can grab a [pre-compiled release](https://github.com/mcataford/doggo/releases) for your machine if one is available or build it locally by cloning the repository and running `go build`.
+
+You can either include the executable in your `$PATH` or run the executable wherever it lives:
+
+```
+doggo <path-to-trace-json> <resource-name> [-vv] [--depth={depth-limit}]
+```
+
+The `resource-name` provided is the resource name associated with the spans that interest you in the provided trace.
+Doggo will display all the span subtrees up to `depth-limit` depth (unlimited depth if not specified) that have a
+resource name that matches your query (either complete or partial).
+
+Default verbosity will include resource names and span duration in millis. Adding `-v` will toss in some extra
+information about each resource and `-vv` will include any metadata (i.e. tagging) that is available in the trace for
+that span.
+
+## Contributing
+
+Doggo welcomes contributions. The main use case is pretty tailored to my day-to-day, but sensible suggested changes are
+welcome!