chore(README): Update it

Signed-off-by: PrajwalCH <prajwal.chapagain58@gmail.com>

README.md

@@ -14,16 +14,18 @@ Checkout the [releases](https://github.com/PrajwalCH/lll/releases) page for pre-
 Usage: lll [options]
 
 Options:
-    -d, --dir PATH      directory to serve (default: current)
-    -p, --port PORT_NUM Port to bind (default: 2058)
-    -h, --help          Display help and exit
+    -d, --dir PATH            Directory to serve (default: current)
+    -p, --port PORT_NUM       Port to bind (default: 2058)
+    -t, --cache-exp-time SECS Cache expiration time in seconds (default: 60)
+    -h, --help                Display help and exit
 ```
 
 ## Building and running
 
 Make sure you installed and setup the [rust toolchain](https://www.rust-lang.org/tools/install) first.
 
-1. Clone this repo `git clone http://github.com/PrajwalCH/lll`
-2. Jump to `lll` dir
-3. Run `cargo build --release` to build it
-4. Then run `cargo run -- [options]` or `./target/release/lll [options]` to start it
+1. Clone this repo `git clone http://github.com/PrajwalCH/lll`.
+2. Jump to `lll` dir.
+3. Run `cargo build --release` to build it.
+4. Then run `cargo run -- [options]` or `./target/release/lll [options]` to start it.
+5. To install run `cargo install --path .` or you can use pre-built binary.