This change configures Dependabot to automatically update the Docker
base images in this repository on a periodic basis.

Dependabot: configure Docker base image updates

Bumps ubuntu from 20.04 to 22.04.

---
updated-dependencies:
- dependency-name: ubuntu
  dependency-type: direct:production
...

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

Bump ubuntu from 20.04 to 22.04

GNU libc v2.38

The name of this branch was changed some time ago, unfortunately this
build configuration was not updated in lock-step.

CI: Rename trunk branch reference

The `go get` command was deprecated in Go v1.17 and is now reserved for use in modules.

```
$ go get github.com/tcnksm/ghr
go: go.mod file not found in current directory or any parent directory.
	'go get' is no longer supported outside a module.
	To build and install a command, use 'go install' with a version,
	like 'go install example.com/cmd@latest'
	For more information, see https://golang.org/doc/go-get-install-deprecation
	or run 'go help get' or 'go help install'.

Exited with code exit status 1
```

Prefer `go install` for modern Go