No root directory found when opening directory with spaces on macOS

When in a directory whose path contains spaces (e.g. `~/Library/Application Support/...`), the extension does not work and emits a lot of messages like this:

```
[Error - 1:27:01 AM] Request textDocument/codeAction failed.
Message: No root directory found
Code: -32603
```

When starting up, the following message is emitted:

```
/Users//Library/Application%20Support/peacememories.mess/2020/9/reason-test/node_modules/.lsp/debug.log
```

The `Application%20Support` directory is also created at that time.
That logs also shows more information about the first log message:

```
Read message
{"jsonrpc":"2.0","id":7,"method":"textDocument/codeAction","params":{"textDocument":{"uri":"file:///Users//Library/Application%20Support/peacememories.mess/2020/9/reason-test/src/Main.re"},"range":{"start":{"line":0,"character":76},"end":{"line":0,"character":76}},"context":{"diagnostics":[]}}}
[server] Got a method textDocument/codeAction
[server] processing took 0.0100135803223ms
Sending response {"id": 7, "jsonrpc": "2.0", "error": {"code": -32603, "message": "No root directory found"}}
```

It seems like some part of the extension uses html escaping for escaping the path, causing the error.

Reproduce the failure by opening the language server in a macOS directory whose path contains spaces, such as ~/Library/Application Support. Start by tracing path handling around the startup log and the textDocument/codeAction root-directory lookup. Done means the extension finds the root directory and serves code actions without the reported errors.

Written by the indexing model from the issue text.