feat: custom branch name templates (#571)

* Add branch-name-template config option

* Logging

* Use branch name template

* Add label to template variables

* Add description template variable

* More concise description for branch_name_template

* Remove more granular time template variables

* Only fetch first label

* Add check for empty template-generated name

* Clean up comments, docstrings

* Merge createBranchTemplateVariables into generateBranchName

* Still replace undefined values

* Fall back to default on duplicate branch

* Parameterize description wordcount

* Remove some over-explanatory comments

* NUM_DESCRIPTION_WORDS: 3 -> 5

src/github/api/queries/github.ts

@@ -18,6 +18,11 @@ export const PR_QUERY = `
         additions
         deletions
         state
+        labels(first: 1) {
+          nodes {
+            name
+          }
+        }
         commits(first: 100) {
           totalCount
           nodes {
@@ -101,6 +106,11 @@ export const ISSUE_QUERY = `
         updatedAt
         lastEditedAt
         state
+        labels(first: 1) {
+          nodes {
+            name
+          }
+        }
         comments(first: 100) {
           nodes {
             id