Add subpage for unreleased ink! 6.x (#352)

* Copy `docs/` to `versioned_docs/version-6.x/`

* Copy `sidebars.js` to `versioned_sidebars/version-6.x-sidebars.json`

* Add 6.x as new version

* Display info notice when viewing unreleased 6.x docs

* Copy `migrating-from-ink-4-to-5.md` to `migrating-from-ink-5-to-6.md`

* Add graphics for title and subpages

* Add initial migration page to sidebar

* Update migration page

docusaurus.config.js

@@ -79,6 +79,11 @@ module.exports = {
           routeBasePath: '/',
           lastVersion: 'current',
           versions: {
+            '6.x': {
+              label: '6.x',
+              path: '6.x',
+              banner: 'none',
+            },
             current: {
               label: '5.x',
               path: '',

src/theme/NavbarItem/DocsVersionDropdownNavbarItem.js

@@ -15,14 +15,31 @@ export default function DocsVersionDropdownNavbarItemWrapper(props) {
         (version) => version.name === 'current',
     );
     const isViewingOutdatedVersion = activeDocContext.activeVersion.name !== currentVersion.name;
+    const isViewingUnreleasedVersion = activeDocContext.activeVersion.name === '6.x';
     const d = 'M256 32c14.2 0 27.3 7.5 34.5 19.8l216 368c7.3 12.4 7.3 27.7 .2 40.1S486.3 480 472 480H40c-14.3 0-27.6-7.7-34.7-20.1s-7-27.8 .2-40.1l216-368C228.7 39.5 241.8 32 256 32zm0 128c-13.3 0-24 10.7-24 24V296c0 13.3 10.7 24 24 24s24-10.7 24-24V184c0-13.3-10.7-24-24-24zm32 224c0-17.7-14.3-32-32-32s-32 14.3-32 32s14.3 32 32 32s32-14.3 32-32z"'
 
-    if (isViewingOutdatedVersion) {
+    if (isViewingUnreleasedVersion) {
         return (
             <>
                 <div className={'navbar__item oldVersion'}>
                     <div className={'attention'}>
-                        <svg xmlns={'http://www.w3.org/2000/svg'} viewBox={'0 0 512 512'}><path d={d}></path></svg>
+                        <svg xmlns={'http://www.w3.org/2000/svg'} viewBox={'0 0 512 512'}>
+                            <path d={d}></path>
+                        </svg>
+                    </div>
+                    You are viewing the documentation for an <em>unreleased</em> version of ink!.
+                </div>
+                <DocsVersionDropdownNavbarItem {...props} />
+            </>
+        );
+    } else if (isViewingOutdatedVersion) {
+        return (
+            <>
+                <div className={'navbar__item oldVersion'}>
+                    <div className={'attention'}>
+                        <svg xmlns={'http://www.w3.org/2000/svg'} viewBox={'0 0 512 512'}>
+                            <path d={d}></path>
+                        </svg>
                     </div>
                     You are viewing the documentation for an older version of ink!.
                 </div>