Make Mermaid JS character limit configurable

[moiflo033]

• Gitea version (or commit ref): 1.14.4
• Git version: 2.30.2
• Operating system: docker
• Log gist:

Description

Currently the character limit is 5000 chars. This isn't enough for more complex diagrams. I understand the concern that mermaid.js might take to long with larger diagramms, hence why i'm suggesting to make it configurable.

Screenshots

[silverwind]

Agree, the 5000 limit was ported from GitLab's implementation, we should add a config option for it.