goreleaser: lowercase binary name (#5765)

and specify files that go into an archive

.goreleaser.yml

@@ -5,7 +5,7 @@ env:
   - GO111MODULE=on
 
 builds:
-  - id: "Tendermint"
+  - id: "tendermint"
     main: ./cmd/tendermint/main.go
     ldflags:
       - -s -w -X github.com/tendermint/tendermint/version.TMCoreSemVer={{ .Version }}
@@ -26,3 +26,11 @@ checksum:
 
 release:
   name_template: "{{.Version}} (WARNING: BETA SOFTWARE)"
+
+archives:
+  files:
+    - LICENSE
+    - README.md
+    - UPGRADING.md
+    - SECURITY.md
+    - CHANGELOG.md