metadata: add Zenodo, tidy badges and keywords (#3373)

* docs: add Zenodo badge

* docs: fix rst image syntax

* docs: collect and re-use badges

* metadata: add zenodo

Fixes #2978

* metadata: sync keywords

* docs: add citation in readme

* docs: one-line badges

.zenodo.json

@@ -0,0 +1,8 @@
+{
+  "title": "DVC: Data Version Control - Git for Data & Models",
+  "keywords": [
+    "data-science", "data-version-control", "machine-learning", "git",
+    "developer-tools", "reproducibility", "collaboration", "ai", "python"],
+  "contributors": [
+    {"name": "DVC team", "type": "Other", "affiliation": "Iterative"}]
+}