feat: update readme

README.md

@@ -3,10 +3,15 @@
 > FIDO(U2F, WebAuthn), YubiKey, OpenPGP command line tool
 
 Install:
-```
+```shell
 cargo install --git https://git.hatter.ink/hatter/card-cli.git
 ```
 
+Compile without features:
+```shell
+cargo build --release --no-default-features
+```
+
 # PGP
 
 ## encrypt & decrypt
@@ -30,7 +35,7 @@ hW53WfImja+b5kwwyqUikyMCAwEAAQ==
 ```
 
 encrypt
-```
+```shell
 $ openssl rsautl -encrypt -pubin -inkey enc_key.pem -in test.txt -out enc.txt -pkcs
 
 OR
@@ -39,7 +44,7 @@ $ openssl pkeyutl -encrypt -inkey enc_key.pem -pubin -in a.txt -out enc.txt
 ```
 
 decrypt
-```
+```shell
 $ card-cli pgp-card-decrypt -c $(cat enc.txt | xxd -ps -c 11111)
 
 OR
@@ -50,7 +55,7 @@ $ card-cli piv-decrypt -s r3 -c "$(cat enc.txt | base64)"
 ## sign & verify
 
 sign
-```
+```shell
 $ card-cli pgp-card-sign -2 $(shasum -a 256 test.txt | awk '{print $1}')
 
 OR
@@ -59,7 +64,7 @@ $ card-cli pgp-card-sign --in test.txt --use-sha256
 ```
 
 verify
-```
+```shell
 $ openssl dgst -sha256 -verify sign_key.pem -signature sig test.txt 
 Verified OK
 ```