Fix invalid empty-state range in getShowingInfo()

[Copilot]

getShowingInfo() always computed startIndex = 1, producing "Showing 1 to 0 of 0 items" when data was empty. The fix returns "No items to show" early when totalItems === 0, before any index arithmetic runs.

Changes

• src/index.ts: In getShowingInfo(), short-circuit with "No items to show" when totalItems === 0 — applies to both normal and filtered data modes.
• src/__tests__/index.test.ts: New test covering the empty-data case.

const table = new EzyTables({ clientEnabled: true, data: [], renderFunction: () => {} });
table.getShowingInfo(); // Previously: "Showing 1 to 0 of 0 items ."
                        // Now:        "No items to show"