DEVOPS-62 updated readme

Author: githubofkrishnadhas

.github/workflows/github_billing_details.yaml

@@ -29,6 +29,8 @@ jobs:
           pip install pipenv
           pipenv install
       - name: execute python program
+        env:
+          GH_TOKEN: ${{ secrets.DEVWITHKRISHNA_PERSONAL_ACCESS_TOKEN }}
         run: |
           pipenv run python3 github_billing.py --organization ${{ inputs.organization }} --account_name ${{ inputs.account_name }}
       - name: send email program

README.md

@@ -11,6 +11,14 @@ This repo uses github rest api to pull billing details for github org and user a
 Later these json files are dropped as an email using sendgrid to ownerof account. Email consists of multiple json atachments
 ```
 
+# Credentials used for authorization
+
+| credential                         | purpose                                                                | check              |
+|------------------------------------|------------------------------------------------------------------------|--------------------|
+| fine grained personal access token | this is used for all purpose like listing repos, github app detailsetc | :heavy_check_mark: |
+| sendgrid api key | this is used for amiling purpose to auth with sendgrid | :heavy_check_mark: |
+
+
 # SendGrid 
 
 ```