feat: add setup & remove cmd for better UX (#43)

* feat: add setup & remove cmd for better UX

* refactor(alias): improve separation of concerns and fix shell sourcing

* chore: remove extra/unused folder

* refactor: introduce separate files for shells

* fix: use temp files for safe shell config modification

internal/alias/zsh.go

@@ -0,0 +1,21 @@
+package alias
+
+type zshShell struct{}
+
+var _ Shell = &zshShell{}
+
+func NewZshShell() (*zshShell, error) {
+	return &zshShell{}, nil
+}
+
+func (z zshShell) Source(rcPath string) string {
+	return defaultShellSource(rcPath)
+}
+
+func (z zshShell) Name() string {
+	return "zsh"
+}
+
+func (z zshShell) Path() string {
+	return ".zshrc"
+}