Fix button and input inconsistent font and style (#4162)

packages/@uppy/core/src/_common.scss

@@ -36,6 +36,8 @@
   all: initial;
   box-sizing: border-box;
   appearance: none;
+  font-family: $font-family-base;
+  line-height: 1;
 }
 
 [dir="rtl"] .uppy-u-reset {

packages/@uppy/provider-views/src/Breadcrumbs.jsx

@@ -7,7 +7,7 @@ const Breadcrumb = (props) => {
     <Fragment>
       <button
         type="button"
-        className="uppy-u-reset"
+        className="uppy-u-reset uppy-c-btn"
         onClick={getFolder}
       >
         {title}

packages/@uppy/provider-views/src/Item/components/ListLi.jsx

@@ -61,7 +61,7 @@ function ListItem (props) {
         // button to open a folder
         <button
           type="button"
-          className="uppy-u-reset uppy-ProviderBrowserItem-inner"
+          className="uppy-u-reset uppy-c-btn uppy-ProviderBrowserItem-inner"
           onClick={handleFolderClick}
           aria-label={i18n('openFolderNamed', { name: title })}
         >

packages/@uppy/provider-views/src/ProviderView/User.jsx

@@ -3,7 +3,7 @@ import { h } from 'preact'
 export default ({ i18n, logout, username }) => {
   return ([
     <span className="uppy-ProviderBrowser-user" key="username">{username}</span>,
-    <button type="button" onClick={logout} className="uppy-u-reset uppy-ProviderBrowser-userLogout" key="logout">
+    <button type="button" onClick={logout} className="uppy-u-reset uppy-c-btn uppy-ProviderBrowser-userLogout" key="logout">
       {i18n('logOut')}
     </button>,
   ])