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## What type of PR is this? (check all applicable)

- [ ] Refactor
- [ ] Feature
- [ ] Bug Fix
- [ ] Optimization
- [X] Documentation Update
- [ ] Go Version Update
- [ ] Dependency Update

## Description

Changed the SPA handler example in README.md in two areas. First, made
sure to actually include the requested path in the call to
`filepath.Join`. Secondly, if the requested path hits a directory, I
think it would be beneficial to also serve the `indexPath` file, and not
list the directory contents. I also edited the comments in the
`README.md` file accordingly.

## Related Tickets & Documents

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- Related Issue #
- Closes #

## Added/updated tests?

- [ ] Yes
- [X] No, and this is why: I only changed the `README.md`, if any tests
are necessary please let me know
- [ ] I need help with writing tests

## Run verifications and test

- [ ] `make verify` is passing
- [ ] `make test` is passing