fix typo

Author: Snawoot

README.md

@@ -163,7 +163,7 @@ Authentication parameters are passed as URI via `-auth` parameter. Scheme of URI
   * `path` - location of file with login and password pairs. File format is similar to htpasswd files. Each line must be in form `<username>:<bcrypt hash of password>`. Empty lines and lines starting with `#` are ignored.
   * `hidden_domain` - same as in `static` provider
   * `reload` - interval for conditional password file reload, if it was modified since last load. Use negative duration to disable autoreload. Default: `15s`.
-* `hmac` - authentication with HMAC-signatures passed as username and password via basic authentication scheme. In that scheme username represents user login as usual and password should be constructed as follows: *password := urlsafe\_base64\_without\_padding(expire\_timestamp || hmac\_sha256(secret, "dumbproxy grant token v1" || username || expire\_timestamp))*, where *expire_timestamp* is 64-bit big-endian UNIX timestamp and *||* is a concatenation operator. [This Python script](https://gist.github.com/Snawoot/2b5acc232680d830f0f308f14e540f1d) can be used a reference implementation of signing. Dumbproxy itself also provides built-in signer: `dumbproxy -hmac-sign <HMAC key> <username> <validity duration>`.
+* `hmac` - authentication with HMAC-signatures passed as username and password via basic authentication scheme. In that scheme username represents user login as usual and password should be constructed as follows: *password := urlsafe\_base64\_without\_padding(expire\_timestamp || hmac\_sha256(secret, "dumbproxy grant token v1" || username || expire\_timestamp))*, where *expire_timestamp* is 64-bit big-endian UNIX timestamp and *||* is a concatenation operator. [This Python script](https://gist.github.com/Snawoot/2b5acc232680d830f0f308f14e540f1d) can be used as a reference implementation of signing. Dumbproxy itself also provides built-in signer: `dumbproxy -hmac-sign <HMAC key> <username> <validity duration>`.
   * `secret` - hex-encoded HMAC secret key. Alternatively it can be specified by `DUMBPROXY_HMAC_SECRET` environment variable. Secret key can be generated with command like this: `openssl rand -hex 32` or `dumbproxy -hmac-genkey`.
   * `hidden_domain` - same as in `static` provider
 * `cert` - use mutual TLS authentication with client certificates. In order to use this auth provider server must listen sockert in TLS mode (`-cert` and `-key` options) and client CA file must be specified (`-cacert`). Example: `cert://`.