Update rule E1022 to allow lists in custom resources

[kddejong]

Issue #, if available:

• Fix E1022 Fn::Join must use a list - fails with CloudFormation Custom Resource #1127

Description of changes:

• Update rule E1022 to allow lists in custom resources

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

Merging #1151 into master will decrease coverage by <.01%.
The diff coverage is 94.11%.

@@            Coverage Diff             @@
##           master    #1151      +/-   ##
==========================================
- Coverage   87.77%   87.76%   -0.01%     
==========================================
  Files         135      135              
  Lines        7997     8007      +10     
  Branches     1966     1970       +4     
==========================================
+ Hits         7019     7027       +8     
- Misses        580      581       +1     
- Partials      398      399       +1

Impacted Files	Coverage Δ
src/cfnlint/__init__.py	89.48% <100%> (+0.06%)	⬆️
src/cfnlint/rules/functions/Join.py	92.17% <90.9%> (-1.41%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 32bc877...013974e. Read the comment docs.