How to apply formatting to a code-generated gmail - google-sheets

Question

I am following these tutorials on how to create an email and populate it with values from a Google Sheet.
https://developers.google.com/apps-script/articles/sending_emails
https://katydecorah.com/code/google-sheets-to-gmail/
It all works as expected, however I cannot apply any formatting to the email such as underline, bold or even tables. Any formatting I apply in the original Google Doc is removed when the email is generated.
EDIT:
Here is the Google-Doc used as the template
Dear {caregiver}
Herewith please find the Weekly Engagement Summary for {fname} {sname}
Week 1: {week_1_score}
Week 2: {week_2_score}
Thank You
And here is the Google-Sheet used with the values
fname|sname|caregiver|email|week_1_score|week_2_score|date drafted
bob|smith|parent1|user1#gmail.com|4|3
john|jones|parent2|user2#gmail.com|2|4
rob|brown|parent3|user3#live.com|3|5
And here is the code-behind script that glue them together and creates the email
// What is the Google Document ID for your email template?
var googleDocId = "<my id>";
// Which column has the email address? Enter the column row header exactly.
var emailField = 'email';
// What is the subject line?
var emailSubject = 'Weekly Engagement Indicator';
// Which column is the indicator for email drafted? Enter the column row header exactly.
var emailStatus = 'date drafted';
/* ----------------------------------- */
// Be careful editing beyond this line //
/* ----------------------------------- */
var sheet = SpreadsheetApp.getActiveSheet(); // Use data from the active sheet
function draftMyEmails() {
var emailTemplate = DocumentApp.openById(googleDocId).getText(); // Get your email template from Google Docs
var data = getCols(2, sheet.getLastRow() - 1);
var myVars = getCols(1, 1)[0];
var draftedRow = myVars.indexOf(emailStatus) + 1;
// Work through each data row in the spreadsheet
data.forEach(function(row, index){
// Build a configuration for each row
var config = createConfig(myVars, row);
// Prevent from drafing duplicates and from drafting emails without a recipient
if (config[emailStatus] === '' || config[emailStatus] !== '' && config[emailField]) {
// Replace template variables with the receipient's data
var emailBody = replaceTemplateVars(emailTemplate, config);
// Replace template variables in subject line
var emailSubjectUpdated = replaceTemplateVars(emailSubject, config);
// Create the email draft
GmailApp.createDraft(
config[emailField], // Recipient
emailSubjectUpdated, // Subject
emailBody // Body
);
sheet.getRange(2 + index, draftedRow).setValue(new Date()); // Update the last column
SpreadsheetApp.flush(); // Make sure the last cell is updated right away
}
});
}
function replaceTemplateVars(string, config) {
return string.replace(/{[^{}]+}/g, function(key){
return config[key.replace(/[{}]+/g, "")] || "";
});
}
function createConfig(myVars, row) {
return myVars.reduce(function(obj, myVar, index) {
obj[myVar] = row[index];
return obj;
}, {});
}
function getCols(startRow, numRows) {
var lastColumn = sheet.getLastColumn(); // Last column
var dataRange = sheet.getRange(startRow, 1, numRows, lastColumn) // Fetch the data range of the active sheet
return dataRange.getValues(); // Fetch values for each row in the range
}
Any help appreciated.
Thanks