bug: injectProps.js not adding Props folder in content folder

[jugshaurya]

Bug:
when new collaborator does npm i, they are not getting src/content/Props folder.

**Problem Details and possible solutions. **

1. combine two exec functions into one
2. Instead of exec use execSync

**Tested? **

• Yes, It is working fine after the above-shown changes.
• Adding both react-native-elements folder and Props Folder at appropriate positions.

Also solve Netlify build problem

[jugshaurya]

@pranshuchittora , review it and fix it by merging PR.

[jugshaurya]

@flyingcircle please review #97