Update the readme me file. Fixed #336

[Flying-Pegasus]

Provided a clear description of where to add the repo name in the constant.js file.

Explanation

Updated the 'Installing the Bot on a Repository' section,
Added the bulletpoints to show step by step process.

The new lines I have added :
3. Add the repository name in the constant.js file:

• Open the constant.js file in the bot's source code.
• Navigate to the checksWhitelist object.
• Add a new entry with your repository name (in lowercase) as the key. The value should define the checks and events specific to your repository.

Example:
If your repository name is my-repo, the checksWhitelist object will look like this:

const checksWhitelist = {
  // Existing entries...
  'my-repo': {
    [openEvent]: [claCheck],
    [reopenEvent]: [],
    [openEventGithubActions]: [claCheckGithubAction],
    [reopenEventGithubActions]: [claCheckGithubAction],
    [synchronizeEvent]: [mergeConflictCheck],
    [closeEvent]: [allMergeConflictCheck],
    [editEvent]: [],
    [issuesLabelEvent]: [],
    [issuesAssignedEvent]: [],
    [pushEvent]: [],
    [pullRequestReviewEvent]: [pullRequestReviewCheck],
    [issueCommentCreatedEvent]: [respondToReviewCheck],
  },
};

4.Save the changes to constant.js.

The more clear explaination is provided in the comments of issue #336 which was approved by the maintainer.

Checklist

• I have successfully deployed my own instance of Oppiabot.
  • You can find instructions for doing this here.
• I have manually tested all the changes made in this PR following the manual tests matrix.

Fixed #336

[seanlip]

@Flying-Pegasus This codebase has no file called constant.js. Could you please double-check that your instructions work as written?

[Flying-Pegasus]

@seanlip Changed constant.js to constants.js from the previous commit. Please review it.

[seanlip]

@Flying-Pegasus Please follow the guidance at https://github.com/oppia/oppia/wiki/Rules-for-making-PRs#step-4-create-a-pull-request for naming your PRs.