Start migration guide (#384)

Merge branch 'master' into docu-start-migration-guide

add migrate-v0.12-to-v0.13.md

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: 6543 <6543@obermui.de>
Reviewed-on: https://gitea.com/gitea/go-sdk/pulls/384
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: techknowlogick <techknowlogick@gitea.io>

docs/migrate-v0.12-to-v0.13.md

@@ -0,0 +1,38 @@
+# Migration Guide: v0.12 to v0.13
+
+v0.13.0 introduces a number of breaking changes, throu it should not be hard to
+migrate.
+Just follow this guid and if issues still ocure ask for help on discord or
+feel free to create an issue.
+
+<!-- toc -->
+
+-   [EditMilestoneOption use StateType (#350)](#EditMilestoneOption-use-StateType)
+-   [RepoSearch Options Struct was rewritten (#346)](#RepoSearch-Options-Struct-was-rewritten)
+
+<!-- tocstop -->
+
+## EditMilestoneOption use StateType
+
+Instead of a raw string StateType is now used for State too.
+just replace old strings with new enum.
+
+
+Pulls:
+
+-   [#350 EditMilestoneOption also use StateType](https://gitea.com/gitea/go-sdk/pulls/350)
+
+
+## RepoSearch Options Struct was rewritten
+
+Since the API itself is ugly and there was no nameconvention whats o ever.
+You easely can pass the wrong options and dont get the result you want.
+
+Now it is rewritten and translated for the API.
+The easyest way to migrate is to look at who this function is used and rewritten that code block.
+
+If there is a special edgecase you have you can pass a `RawQuery` to the API endpoint.
+
+Pulls:
+
+-   [#346 Refactor RepoSearch to be easy usable](https://gitea.com/gitea/go-sdk/pulls/346)