Update issue templates

Create a template for adding a new LSH family to the project.

Author: kernelmethod

.github/ISSUE_TEMPLATE/add-new-lsh-family.md

@@ -0,0 +1,17 @@
+---
+name: Add new LSH family
+about: Request to add a new LSH family to the project
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**What similarity measure is this hash function for?**
+What similarity function does this LSH family apply to?
+
+**Describe the hash function**
+Go in more depth on the hash function. If your LSH family is for a similarity function that's already supported by this package, you should describe any features or advantages it has that would make it better than (or a useful alternative to) the existing LSH family that's supported by this package.
+
+**References**
+Please provide references that describe the hash function family. You can also add links to other concepts (e.g. the similarity function that the LSH family applies to) if you think it'd help us determine whether or not to add the LSH family to the package.