Tag v2 to differenciate from github.com/google/btree

Signed-off-by: Sylvain Rabot <[email protected]>

README.md

@@ -7,11 +7,11 @@ The API is based off of the wonderful
 https://pkg.go.dev/github.com/petar/GoLLRB/llrb, and is meant to allow btree to
 act as a drop-in replacement for gollrb trees.
 
-See https://pkg.go.dev/sylr.dev/btree for documentation.
+See https://pkg.go.dev/sylr.dev/btree/v2 for documentation.
 
 ## Fork disclaimer
 
-`sylr.dev/btree` is a fork of [`github.com/google/btree`](https://github.com/google/btree)
+`sylr.dev/btree/v2` is a fork of [`github.com/google/btree`](https://github.com/google/btree)
 with the following adaptations:
 
 - The copy-on-write mechanism has been removed

go.mod

@@ -12,6 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-module sylr.dev/btree
+module sylr.dev/btree/v2
 
 go 1.20