Adding support for snapshots

[pgoslatara]

Resolves #333

Problem

Solution

Checklist

• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
src/dbt_bouncer
config_file_validator.py	107	2	98%	160, 190
runner.py	75	4	95%	133, 169–170, 228
utils.py	102	14	86%	52, 146–160, 199
src/dbt_bouncer/artifact_parsers
parsers_common.py	47	1	98%	59
parsers_manifest.py	94	4	96%	190, 192, 200, 293
parsers_run_results.py	33	3	91%	64, 66, 69
src/dbt_bouncer/checks/manifest
check_models.py	201	1	99%	546
check_unit_tests.py	47	3	94%	100, 150, 201
src/dbt_bouncer/checks/run_results
check_run_results.py	19	2	89%	97–98
TOTAL	4042	34	99%

Tests	Skipped	Failures	Errors	Time
1	0 💤	0 ❌	0 🔥	8.347s ⏱️