I would suggest enclosing the svg within a div element, as you have used the viewBox attribute in the svg, it will resize proportionally.
Check out this code snippet:
<div class="wrap">
<svg viewBox="0 0 300 349" xmlns="http://www.w3.org/2000/svg">
<path class="path" fill-rule="evenodd" clip-rule="evenodd"
d="M0 20C0 8.9543 8.95431 0 20 0H280C291.046 0 300 8.95431 300 20V187.023C300 194.606 295.711 201.537 288.925 204.921L0 349V20Z"></path>
</svg>
</div>
I have removed the width and height attributes from the svg, as well as the fill attribute from the path and added a class attribute so that you can adjust the wrapper's size and path color using the following CSS:
.wrap {
width: 500px; /* the height will adjust proportionally based on the viewBox */
}
.path {
fill: red; /* specify the desired color */
}
Below is a CSS shape resembling the svg design:
.box {
width: 300px;
height: 200px;
background-color: #5795fa;
border-top-left-radius: 20px;
border-top-right-radius: 20px;
border-bottom-left-radius: 0px;
border-bottom-right-radius: 0px;
position: relative;
}
.box::after {
content: " ";
display: block;
position: absolute;
left: 0px;
top: 100%;
height: 0;
border-top: 30px solid #5795fa;
border-left: 150px solid #5795fa;
border-bottom: 30px solid transparent;
border-right: 150px solid transparent;
}
<div class="box"></div>