Fix markdown lint errors

Feature-Set.md

@@ -1,4 +1,5 @@
-<!-- markdownlint-disable-next-line MD041 -->
+<!-- markdownlint-disable-next-line first-line-h1 -->
+
 ##### Project
 
 ::PROJECT-NAME
@@ -25,24 +26,24 @@ feature set by priority, functional area, actor, business object, or
 release can help identify missing, extra, or poorly motivated features
 early.
 
-*TODO: Before writing individual feature descriptions, list all the
+_TODO: Before writing individual feature descriptions, list all the
 features that you think you will need. Organize them so that missing
 features appear as blanks on this page, and extra features will appear
 to be extras that don't fit anywhere. See the
 [feature format](Feature-Format#further-information) document for more
-tips on specifying features and feature sets.*
+tips on specifying features and feature sets._
 
-*TIP: Refer back to the user stories in your [user needs](User-Needs)
+_TIP: Refer back to the user stories in your [user needs](User-Needs)
 document and to the [use case suite](Use-Case-Suite).
-Use them for ideas and make sure that you cover all of them.*
+Use them for ideas and make sure that you cover all of them._
 
 ### Features by Release and Priority
 
-*TODO: Select subset of features can be implemented for a given release.
+_TODO: Select subset of features can be implemented for a given release.
 When features are listed in priority order, choosing the features to
 implement in a release simply becomes a matter of "drawing a line":
 features below the line must wait for a later release. Make sure to also
-consider estimated effort and risk.*
+consider estimated effort and risk._
 
 - ::Release 1.0
   - ::Essential