PLT-639: Adding gitleaks MBI scanning & updating gitleaks pre-commit version (#211)

## 🎫 Ticket

https://jira.cms.gov/browse/...

## 🛠 Changes

<!-- What was added, updated, or removed in this PR? -->

Gitleaks custom config extension was added (.gitleaks.toml) allowing for
a regex-based MBI filter to be run against new commits, and the gitleaks
pre-commit version was updated to 8.19.x which doesn't affect us at this
time.

## ℹ️ Context

<!-- Why were these changes made? Add background context suitable for a
non-technical audience. -->

Bulk API Platform Team has an ongoing goal of improving security and
safeguarding PHI/PII for our members, to that end we are applying a
belt-and-suspenders approach to preventing leakage of data (such as
Medicare Beneficiary Identifiers) in github.

<!-- If any of the following security implications apply, this PR must
not be merged without Stephen Walter's approval. Explain in this section
and add @SJWalter11 as a reviewer.
  - Adds a new software dependency or dependencies.
  - Modifies or invalidates one or more of our security controls.
  - Stores or transmits data that was not stored or transmitted before.
- Requires additional review of security implications for other reasons.
-->

##   Validation

<!-- How were the changes verified? Did you fully test the acceptance
criteria in the ticket? Provide reproducible testing instructions and
screenshots if applicable. -->

These changes were tested locally and automatically as they make
modifications to the pre-commit functionality, and were initially tested
and validated against a pregenerated file with MBI data in PLT-532.

Author: ildesenesence

.gitleaks.toml

@@ -0,0 +1,9 @@
+title = "DASG Standard"
+
+[extend]
+  useDefault = true
+
+[[rules]]
+  id = "mbi-detection"
+  description = "Detects a potential MBI pattern based on https://www.cms.gov/medicare/new-medicare-card/understanding-the-mbi.pdf"
+  regex = '''\b((?i)[1-9][ACDEFGHJKMNPQRTUVWXY][ACDEFGHJKMNPQRTUVWXY\d]-?\d[ACDEFGHJKMNPQRTUVWXY][ACDEFGHJKMNPQRTUVWXY\d]\d-?[ACDEFGHJKMNPQRTUVWXY]{2}\d{2})\b'''

.pre-commit-config.yaml

@@ -1,5 +1,5 @@
 repos:
   - repo: https://github.com/gitleaks/gitleaks
-    rev: v8.16.1
+    rev: v8.19.2
     hooks:
       - id: gitleaks