add clear button to clear the sql window

main.go

@@ -551,6 +551,7 @@ sqlfmt was inspired by <a href="https://prettier.io/">prettier</a>. It is based
 		<br><input type="radio" name="casemode" value="title" onChange="range()" onInput="range()" id="casemode3"><label for="casemode3">Title</label>
 		<input type="radio" name="casemode" value="spongebob" onChange="range()" onInput="range()" id="casemode4"><label for="casemode4">sPOngEboB</label>
 		<span class="jsonly"><br><button type="button" onClick="resetVals()" id="reset">reset to defaults</button></span>
+		<span class="jsonly"><br><button type="button" onClick="clearSQL()" id="clear">clear</button></span>
 	</div>
 </div>
 
@@ -596,6 +597,11 @@ function resetVals() {
 	range();
 }
 
+function clearSQL() {
+	sqlEl.value = '';
+	range();
+}
+
 // https://stackoverflow.com/questions/400212/how-do-i-copy-to-the-clipboard-in-javascript
 function copyTextToClipboard(text) {
 	const textArea = document.createElement('textarea');