Add shell completion templates and manpage template

src/templates/completion-zsh.handlebars

@@ -0,0 +1,39 @@
+#compdef _{{spec.name}} {{spec.name}}
+# Zsh completion for {{spec.name}}
+# Auto-generated by cli-spec-generator
+
+_{{_name}}() {
+    local line
+
+    _arguments -C \
+        '(-h --help)'{-h,--help}'[Show help]' \
+        '(-v --version)'{-v,--version}'[Show version]' \
+        {{#each spec.globalOptions}}
+        '{{#if short}}-{{short}}, {{/if}}--{{name}}[{{escape description}}]' \
+        {{/each}}
+        {{#each spec.commands}}
+        '{{name}}[{{escape description}}]' \
+        {{/each}}
+        '*::arg:->args'
+
+    if [[ -z "$line" ]]; then
+        return
+    fi
+
+    local cmd="${line[1]}"
+    shift line
+
+    case "$cmd" in
+        {{#each spec.commands}}
+        {{name}})
+            _arguments \
+                {{#each options}}
+                '{{#if short}}-{{short}}, {{/if}}--{{name}}[{{escape description}}]' \
+                {{/each}}
+                '*::arg:->args'
+            ;;
+        {{/each}}
+    esac
+}
+
+_{{_spec.name}} "$@"