feat: enable you to create a follow up pr file

[suzuki-shunsuke]

Close #1799

If terraform apply fails, create-follow-pr action creates or updates a file .tfaction/failed-prs in the working directory and creates a follow up pull request.

e.g.

# This file is created and updated by tfaction for follow up pull requests.
# You can remove this file safely.
https://github.com/suzuki-shunsuke/terraform-example/pull/1

• document: add the description about .tfaction/failed-prs tfaction-docs#465

[suzuki-shunsuke]

https://github.com/suzuki-shunsuke/tfaction/releases/tag/v1.6.0-2

[suzuki-shunsuke]

Removed the setting and change the default behaviour.

[suzuki-shunsuke]

https://github.com/suzuki-shunsuke/tfaction/releases/tag/v1.6.0-4

[suzuki-shunsuke]

Create a directory .tfaction

Rename the file .tfaction-failed-prs to .tfaction/failed-prs.

Even if we will need to add other files related to tfaction, we can avoid cluttering up working directories.

[suzuki-shunsuke]

About conflict

.tfaction/failed-prs may cause conflicts.
To avoild conflicts, we can change file names per pull request like .tfaction/failed-pr-<pr number>.
If conflicts would be troublesome, we need to consider this kind of approach, but for now I think the conflict is not bad.
The conflict clarifies that others are working in the same working directory.
And the conflict encourages users to update branches.

[suzuki-shunsuke]

https://github.com/suzuki-shunsuke/tfaction/releases/tag/v1.6.0-5