output_generator: markdown-gallery not work in best-of-update-action version 0.8.5

[jiandongj]

Describe the bug:

output_generator: markdown-gallery not work in current version (0.8.5).

Expected behaviour:

output_generator should support "markdown-gallery", not only "markdown-list" in this configuration: https://github.com/best-of-lists/best-of-generator#configuration-options

Steps to reproduce the issue:

Follow best-of-streamlit repo's projects.yml, and update github workflow best-of-update-action to version 0.8.5, when trigger action this bug happend.

Technical details:

• Host Machine OS (Windows/Linux/Mac):

Possible Fix:

Additional context:

markdown-gallery feature was introduced by this pr: #29