refactor(starter): upgrade to new version of gatsby

internal/gatsby/utils/concat.ts

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+const concat = (...args: string[]): string => args.join("");
+
+export default concat;

internal/gatsby/utils/decrement.ts

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+const decrement = (n: number): number => n - 1;
+
+export default decrement;

internal/gatsby/utils/increment.ts

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+const increment = (n: number): number => n + 1;
+
+export default increment;

internal/gatsby/utils/index.ts

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+export { default as toKebabCase } from "./to-kebab-case";
+export { default as decrement } from "./decrement";
+export { default as increment } from "./increment";
+export { default as concat } from "./concat";

internal/gatsby/utils/to-kebab-case.ts

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+const toKebabCase = (str: string = ""): string => str.toLowerCase()
+  .replace(/[^\w\s]/gi, "")
+  .split(" ").join("-")
+  .split("_").join("-");
+
+export default toKebabCase;