feat: add support ofr default value syntax

- Introduced a new script `test-default-values.js` to validate default value syntax in commands.
- Updated `package.json` to include the new test script in the e2e test command.
- Modified GitHub Actions workflow to run the new e2e tests.
- Enhanced `commandConvert` function to support default value syntax in environment variables.
- Added unit tests for the new functionality in `command-default-values.test.ts`.

fix(release): manually release a major version

There was an issue with a major release, so this manual-releases.md
change is to release a new major version.

Reference: #261

BREAKING CHANGE: I will fix up these notes soon.

fix(release): manually release a major version

There was an issue with a major release, so this manual-releases.md
change is to release a new major version.

Reference: #261

BREAKING CHANGE: I will fix up these notes soon.

chore(ci): add back semantic-release

fix(readme): update readme badges

docs: add dsbert as a contributor (#260)

* docs: update README.md [skip ci]

* docs: update .all-contributorsrc [skip ci]

Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

Revert "fix: signal handling (#227)"

This reverts commit 8a9cf0e.

fix: signal handling (#227)

Signals should delegate to the child process to determine what to
do as cross-env is a facade to spawning them cross platform.

SIGINT, in particular, can decide swallow the signal and continue on.

cross-env needs to wait for the child to decide when it's time to exit.

fixed leaking `process.on` listeners.

Co-authored-by: Kent C. Dodds <me+github@kentcdodds.com>

feat: update dependencies (#223)

* Update dependencies

BREAKING CHANGE: Drop Node 8 support

fix: do not compile anything