add velero.io site content, move docs to under site/docs (#1489)

* Adding in Jekyll site | Adjusting gitignore for Jekyll build | Moving docs to site folder

Signed-off-by: Lee Springer <lee@smalltalk.agency>

Adding in Jekyll site | Adjusting gitignore for Jekyll build | Moving docs to site folder

Signed-off-by: Lee Springer <lee@smalltalk.agency>

* Restore main.go to original location

Signed-off-by: Lee Springer <lee@smalltalk.agency>

* Updates to footer

Signed-off-by: Lee Springer <lee@smalltalk.agency>

* Updates to homepage links

Signed-off-by: Lee Springer <lee@smalltalk.agency>

* Content updates

Signed-off-by: Lee Springer <lee@smalltalk.agency>

site/_data/default.yml

@@ -0,0 +1,30 @@
+toc:
+  - title: User Guide
+    subfolderitems:
+      - page: Concepts
+        url: /concepts
+      - page: Build from scratch
+        url: /build-from-scratch
+      - page: Cloud provider specifics
+        url: /cloud-provider-specifics
+      - page: Debugging restores
+        url: /debugging-restores
+      - page: FAQ
+        url: /faq
+  - title: Reference
+    subfolderitems:
+      - page: CLI reference
+        url: /cli-reference/index
+      - page: Config definition
+        url: /config-definition
+      - page: Output file format
+        url: /output-file-format
+      - page: Sample YAML files
+        url: /examples
+        github: true
+  - title: Scenarios
+    subfolderitems:
+      - page: Disaster Recovery
+        url: /use-cases
+      - page: Cluster migration
+        url: /use-cases.html#cluster-migration