Bugfix mermaid diagram title is 'undefined' on GHES

[Kesin11]

At least GHES v3.8 occurs this bug.
To fix it, we get mermaid gantt chart name from workflow_run API result.

[github-actions]

Code Metrics Report

	main (838e853)	#25 (766d58d)	+/-
Coverage	0.0%	0.0%	0.0%
Test Execution Time	1s	2s	+1s

Details

  |                     | main (838e853) | #25 (766d58d) | +/-  |
  |---------------------|----------------|---------------|------|
  | Coverage            |           0.0% |          0.0% | 0.0% |
  |   Files             |              0 |             0 |    0 |
  |   Lines             |              0 |             0 |    0 |
  |   Covered           |              0 |             0 |    0 |
- | Test Execution Time |             1s |            2s |  +1s |

dist_size

	main (838e853)	#25 (766d58d)	+/-
post.js	1307466byte	1307450byte	-16byte
main.js	55byte	55byte	0byte

---

Reported by octocov