Fix `route-base-path` option not including `index.html` in the url

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (0dbf2d6) 100.00% compared to head (f52ce56) 100.00%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #35 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 42 43 +1 Lines 432 436 +4 Branches 65 66 +1 ========================================= + Hits 432 436 +4 ``` | [Files Changed](https://app.codecov.io/gh/imjuni/erdia/pull/35?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ByungJoon+Lee) | Coverage Δ | | |---|---|---| | [src/tools/getSlashEndRoutePath.ts](https://app.codecov.io/gh/imjuni/erdia/pull/35?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ByungJoon+Lee#diff-c3JjL3Rvb2xzL2dldFNsYXNoRW5kUm91dGVQYXRoLnRz) | `100.00% <100.00%> (ø)` | |

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