Update the Readme with instructions

Author: tamalchowdhury

.env.sample

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+TELEGRAM_BOT_TOKEN=telegram_bot_token
+TELEGRAM_CHAT_ID=telegram_chat_id
+ACCOUNT_NO=desco_account_number

README.md

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+# DESCO Balance Bot Script
+
+## Setting up Locally:
+
+- You need `Python 3` installed on your computer
+
+Install the following Python dependencies:
+
+```bash
+pip install requests python-dotenv
+```
+
+Rename the `.env.sample` file to `.env` file:
+
+```bash
+mv .env.sample .env
+```
+
+## Setting up the Telegram bot:
+
+1. Open Botfather https://t.me/botfather and follow the instructions to create your bot (e.g, Desco Balance Bot). You will get a telegram bot token. 
+2. Copy and add it to `TELEGRAM_BOT_TOKEN` in the `.env` file.
+3. Send a `hi/hello` chat to your new bot.
+4. Open this URL in your browser `https://api.telegram.org/bot{TELEGRAM_BOT_TOKEN}/getUpdates`
+5. Copy the chat `id` value and add it to the `TELEGRAM_CHAT_ID` in the `.env` file.
+
+## Run the script:
+
+```bash
+python check_balance.py
+```
+
+Output:
+
+```bash
+/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/site-packages/urllib3/connectionpool.py:1097: InsecureRequestWarning: Unverified HTTPS request is being made to host 'prepaid.desco.org.bd'. Adding certificate verification is strongly advised. See: https://urllib3.readthedocs.io/en/latest/advanced-usage.html#tls-warnings
+  warnings.warn(
+
+(True, 'Telegram sent')
+```
+
+Ignore the SSL warning for now (I will update it later); you should see (True, 'Telegram sent`)
+
+And receive a message in your Telegram app.
+
+## Known issues:
+
+It is possible that behind the scenes, DESCO is using multiple endpoints for quering various Meter types.
+
+The endpoint this script is using is:
+
+```text
+https://prepaid.desco.org.bd/api/unified/customer/getBalance?accountNo=
+```
+
+So please test this endpoint with your DESCO account and first verify that this is working for your meter.