Issue templates directory (#11450)

* Issue templates

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add some comments, appease the linter

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add docs and re-use dir candidates

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add default labels to issue templates

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Generate swagger

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Suggested changes

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Update issue.go

* Suggestions

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Extract metadata from legacy if possible

Signed-off-by: jolheiser <john.olheiser@gmail.com>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

routers/api/v1/api.go

@@ -866,6 +866,7 @@ func RegisterRoutes(m *macaron.Macaron) {
 							Delete(reqToken(), repo.DeleteTopic)
 					}, reqAdmin())
 				}, reqAnyRepoReader())
+				m.Get("/issue_templates", context.ReferencesGitRepo(false), repo.GetIssueTemplates)
 				m.Get("/languages", reqRepoReader(models.UnitTypeCode), repo.GetLanguages)
 			}, repoAssignment())
 		})