[skip ci] Create build from source doc

# Install Milvus from Source Code

## Software requirements

- Ubuntu 18.04 or higher

- CMake 3.14 or higher

- CUDA 10.0 or higher

- NVIDIA driver 418 or higher

## Compilation

### Step 1 Install dependencies

```shell

$ cd [Milvus sourcecode path]/core

$ ./ubuntu_build_deps.sh

```

### Step 2 Build

```shell

$ cd [Milvus sourcecode path]/core

$ ./build.sh -t Debug

or 

$ ./build.sh -t Release

```

When the build is completed, all the stuff that you need in order to run Milvus will be installed under `[Milvus root path]/core/milvus`.

## Launch Milvus server

```shell

$ cd [Milvus root path]/core/milvus

```

Add `lib/` directory to `LD_LIBRARY_PATH`

```

$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/path/to/milvus/lib

```

Then start Milvus server:

```

$ cd scripts

$ ./start_server.sh

```

To stop Milvus server, run:

```shell

$ ./stop_server.sh

```