feat(config): add ignore_tags option

[kenji-miyake]

Resolves (#36)

Description

As discussed in #36, added ignore_tags option.

Motivation and Context

Sometimes users want to carry over commits instead of dropping them as skip_tags option does.

How Has This Been Tested?

Just tested in my local environment.

Although I tried to add tests in changelog.rs and integration_tests.rs, I thought it's impossible to test ignore_tags there.
I'd like to discuss in this PR a way to add automated tests.

Screenshots / Output (if appropriate):

$ git clone [email protected]:kenji-miyake/git-cliff.git
$ cd git-cliff
$ cargo run | tail -n 30
(omitted)
## [0.1.0-beta.2] - 2021-06-14

### Bug Fixes

- Install musl-tools for musl builds

$ git checkout add-ignore-tags
$ sd 'ignore_tags = ""' 'ignore_tags = "v0.1.0-beta.2"' config/cliff.toml
$ cargo run | tail -n 30
(omitted)
## [0.1.0-beta.3] - 2021-06-14

### Bug Fixes

- Install musl-tools for musl builds

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[kenji-miyake]

Tentatively, I've added a test using GitHub Actions. ee85a9b
@orhun Do you have any other ideas to test this?

[orhun]

Overall LGTM! I just have a question and a few minor requests.

[orhun]

Tentatively, I've added a test using GitHub Actions. ee85a9b @orhun Do you have any other ideas to test this?

Absolutely liked this approach. I think we can leave it as is, just one suggestion: maybe rename the folder as fixtures and also rename the workflow to something like test-fixtures? I'm not sure though.

About the unit tests, I think I can work on that after merging the PR.

[orhun]

Neat implementation. Thank you!