fix([README.md]): typos in README.md causes installation error

The following description in README.md might causes ambiguous parsing during cmake code building:

cmake -DLWS_WITHOUT_TESTAPPS=ON -DLWS_WITHOUT_TEST_SERVER=ON-DLWS_WITHOUT_TEST_SERVER_EXTPOLL=ON.

split -D from SERVER=ON

Author: rexlim820220

README.md

@@ -21,7 +21,7 @@ git clone https://libwebsockets.org/repo/libwebsockets --depth 1 --branch v4.2-s
 cd libwebsockets
 mkdir build
 cd build
-cmake -DLWS_WITHOUT_TESTAPPS=ON -DLWS_WITHOUT_TEST_SERVER=ON-DLWS_WITHOUT_TEST_SERVER_EXTPOLL=ON \
+cmake -DLWS_WITHOUT_TESTAPPS=ON -DLWS_WITHOUT_TEST_SERVER=ON -DLWS_WITHOUT_TEST_SERVER_EXTPOLL=ON \
       -DLWS_WITHOUT_TEST_PING=ON -DLWS_WITHOUT_TEST_CLIENT=ON -DCMAKE_C_FLAGS="-fpic" -DCMAKE_INSTALL_PREFIX=/usr/local ..
 make
 sudo make install