[#2291] Support the '...' group for alphabetizing fragment spreads

Description

Adds a group type to the groups property of the alphabetize rule indicating where fragment spreads should be in a selection set.

Similarly to the '*' group, which stands for "everything else," the '...' stands for "all fragment spreads."

Fixes #2291

Type of change

[x] New feature (non-breaking change which adds functionality)
[x] This change requires a documentation update

How Has This Been Tested?

Added the following unit tests, ran yarn test and verified that the error messages match the expected ones:

[x] should sort selections by group when ... is at the start
[x] should sort selections by group when ... is between
[x] should sort selections by group when ... is at the end

Checklist:

[x] I have followed the CONTRIBUTING doc and the style guidelines of this project
[x] I have performed a self-review of my own code
[x] I have commented my code, particularly in hard-to-understand areas
[x] I have made corresponding changes to the documentation
[x] My changes generate no new warnings
[x] I have added tests that prove my fix is effective or that my feature works
[x] New and existing unit tests and linter rules pass locally with my changes
[ ] Any dependent changes have been merged and published in downstream modules

Further comments

When working on this change, the display name for a fragment spread was showing undefined <fragment name>, which was because there was no name mapping for that Kind — so I went ahead and added display names for all Kind values, and sorted the map.

dimaMachina / graphql-eslint