Explicitely prohibit space and special character in theme names

src/bin/shared/buildContext.ts

@@ -468,6 +468,7 @@ export function getBuildContext(params: {
         process.exit(-1);
     }
 
+    const themeNames = ((): [string, ...string[]] => {
         const themeNames = ((): [string, ...string[]] => {
             if (buildOptions.themeName === undefined) {
                 return parsedPackageJson.name === undefined
@@ -491,6 +492,23 @@ export function getBuildContext(params: {
             return [mainThemeName, ...themeVariantNames];
         })();
 
+        for (const themeName of themeNames) {
+            if (!/^[a-zA-Z0-9_-]+$/.test(themeName)) {
+                console.error(
+                    chalk.red(
+                        [
+                            `Invalid theme name: ${themeName}`,
+                            `Theme names should only contain letters, numbers, and "_" or "-"`
+                        ].join(" ")
+                    )
+                );
+                process.exit(-1);
+            }
+        }
+
+        return themeNames;
+    })();
+
     const projectBuildDirPath = (() => {
         webpack: {
             if (bundler !== "webpack") {