Adding support for stdin input in the encode64 plugin

plugins/encode64/encode64.plugin.zsh

-encode64(){ printf '%s' $1 | base64 }
-decode64(){ printf '%s' $1 | base64 --decode }
+encode64() {
+    if [[ $# -eq 0 ]]; then
+        cat | base64
+    else
+        printf '%s' $1 | base64
+    fi
+}
+
+decode64() {
+    if [[ $# -eq 0 ]]; then
+        cat | base64 --decode
+    else
+        printf '%s' $1 | base64 --decode
+    fi
+}
 alias e64=encode64
 alias d64=decode64