Add README

Include short details on using the library.

README.md

@@ -0,0 +1,22 @@
+# get-form-values
+
+Get the value of a form using `HTMLFormElement.elements`.
+
+## Usage
+
+```typescript
+import getFormValues from '@theoryofnekomata/get-form-values';
+
+const form = document.getElementById('form')
+
+// optional, but just in case there are multiple submit buttons in the form,
+// individual submitters can be considered
+const submitter = form.querySelector('[type="submit"]')
+
+const values = getFormValues(form, submitter)
+```
+
+## Tests
+
+The library has been tested on JSDOM through Jest, and the real DOM using
+Cypress.