fix: enable spellcheck prop in textarea (#391)

packages/tldraw/src/state/shapes/StickyUtil/StickyUtil.tsx

                 autoCorrect="false"
                 autoSave="false"
                 autoFocus
-                spellCheck={false}
+                spellCheck={true}
                 alignment={shape.style.textAlign}
               />
             )}

packages/tldraw/src/state/shapes/TextUtil/TextUtil.tsx

                   onKeyDown={handleKeyDown}
                   onBlur={handleBlur}
                   onPointerDown={handlePointerDown}
+                  spellCheck="true"
                   wrap="off"
                   dir="auto"
                   datatype="wysiwyg"