fix: allow independent execution of build and test scripts

Author: Mathieu Davy

package.json

@@ -8,7 +8,14 @@
     ],
     "scripts": {
         "install": "cd src/danfojs-base && yarn && cd ../danfojs-browser && yarn && cd ../danfojs-node && yarn",
-        "build": "cd src/danfojs-node && yarn build:clean && cd ../danfojs-browser && yarn build:clean",
-        "test": "cd src/danfojs-base && yarn && cd ../danfojs-node && yarn && yarn test:clean && cd ../danfojs-browser && yarn && yarn test:clean"
+        "build": "yarn build:browser && yarn build:node",
+        "build:browser": "cd src/danfojs-browser && yarn build:clean",
+        "build:node": "cd src/danfojs-node && yarn build:clean",
+        "pretest": "cd src/danfojs-base && yarn",
+        "test": "yarn test:browser && yarn test:node",
+        "pretest:browser": "yarn pretest",
+        "test:browser": "cd src/danfojs-browser && yarn && yarn test:clean",
+        "pretest:node": "yarn pretest",
+        "test:node": "cd src/danfojs-node && yarn && yarn test:clean"
     }
 }