Prepare release v0.15.0 (golang-templates#134)

Move main package to root and add Docker image (golang-templates#127)

- Move main package to root.
- Update golanci-lint configuration.
- Build and push Docker container image.
- Refine GitHub Actions workflow.

Add license badge (golang-templates#123)

Update golangci-lint configuration (golang-templates#121)

Use main branch (golang-templates#116)

Update to Go 1.16 (golang-templates#111)

Add CodeQL analysis to GitHub workflow (golang-templates#66)

Remove mvdan.cc/gofumpt from tools (golang-templates#102)

Bump github.com/goreleaser/goreleaser from 0.150.0 to 0.151.1 in /too…

…ls (golang-templates#93)

Bumps [github.com/goreleaser/goreleaser](https://github.com/goreleaser/goreleaser) from 0.150.0 to 0.151.1.
- [Release notes](https://github.com/goreleaser/goreleaser/releases)
- [Changelog](https://github.com/goreleaser/goreleaser/blob/master/.goreleaser.yml)
- [Commits](goreleaser/goreleaser@v0.150.0...v0.151.1)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Add Codecov integration (golang-templates#89)