Create README.md

Add and edit README.md file from https://github.com/whitebatman2/rtl8821CU/blob/master/README.md

README.md

@@ -0,0 +1,59 @@
+# Realtek RTL8811CU/RTL8821CU version 5.4.1 USB wifi adapter driver for Linux 4.20.x
+
+Before build this driver make sure `make`, `gcc`, `linux-header` and `git` have been installed in your system
+
+## Build and install with DKMS
+
+DKMS is a system which will automatically recompile and install a kernel module when a new kernel gets installed or updated. To make use of DKMS, install the dkms package.
+
+### Debian/Ubuntu:
+
+    sudo apt-get install dkms
+
+### Arch Linux/Manjaro:
+
+    sudo pacman -S dkms
+
+To make use of the DKMS feature with this project, do the following:
+
+    DRV_NAME=rtl8821CU
+    DRV_VERSION=5.4.1
+    git clone https://github.com/brektrou/rtl8821CU.git
+    sudo cp -r ${DRV_NAME} /usr/src/${DRV_NAME}-${DRV_VERSION}
+    sudo chown -hRv root:root /usr/src/${DRV_NAME}-${DRV_VERSION}
+    sudo dkms add -m ${DRV_NAME} -v ${DRV_VERSION}
+    sudo dkms build -m ${DRV_NAME} -v ${DRV_VERSION}
+    sudo dkms install -m ${DRV_NAME} -v ${DRV_VERSION}
+
+If you later on want to remove it again, do the following:
+
+    DRV_NAME=rtl8821CU
+    DRV_VERSION=5.4.1
+    sudo dkms remove ${DRV_NAME}/${DRV_VERSION} --all
+
+## Build and install without DKMS
+Use following commands in source directory:
+```
+make
+sudo make install
+```
+## Raspberry Pi
+To build this driver on Raspberry Pi you need to set correct platform in Makefile.
+Change
+```
+CONFIG_PLATFORM_I386_PC = y
+CONFIG_PLATFORM_ARM_RPI = n
+CONFIG_PLATFORM_ARM_RPI3 = n
+```
+to
+```
+CONFIG_PLATFORM_I386_PC = n
+CONFIG_PLATFORM_ARM_RPI = y
+CONFIG_PLATFORM_ARM_RPI3 = n
+```
+For the Raspberry Pi 3 you need to change it to
+```
+CONFIG_PLATFORM_I386_PC = n
+CONFIG_PLATFORM_ARM_RPI = n
+CONFIG_PLATFORM_ARM_RPI3 = y
+```