feat: add gron greppable output format

[danielgtaylor]

This PR adds the awesome gron format as a built-in output format for Restish. It makes it easy to explore new or rarely used APIs right from the terminal by enabling easy grepping that includes structured path information in the output. Use it via:

# Gron output example
$ restish api.rest.sh/types -o gron
HTTP/2.0 200 OK
...

body = {};
body.$schema = "https://api.rest.sh/schemas/TypesModel.json";
body.boolean = true;
body.integer = 42;
body.nullable = null;
body.number = 123.45;
body.object = {};
body.object.binary = "3q3A3g==";
body.object.binary_long = "AAECAwQFBgcICQoLDA0ODw==";
body.object.date = "2023-06-17T00:00:00Z";
body.object.date_time = "2023-06-17T16:16:35.74384951Z";
body.object.url = "https://rest.sh/";
body.string = "Hello, world!";
body.tags = [];
body.tags[0] = "example";
body.tags[1] = "short";

# Easy to grep and see the path/structure
$ restish api.rest.sh/types -o gron | grep date
body.object.date = "2023-06-17T00:00:00Z";
body.object.date_time = "2023-06-17T16:16:48.840596241Z";

[codecov[bot]]

Codecov Report

Merging #196 (1a9df79) into main (d9c4f96) will increase coverage by 0.60%. The diff coverage is 98.87%.

Additional details and impacted files

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