docs(CONTRIBUTING): one LGTM for maintainers

Signed-off-by: Matthew Fisher <matt.fisher@microsoft.com>

CONTRIBUTING.md

@@ -263,6 +263,8 @@ Like any good open source project, we use Pull Requests (PRs) to track code chan
     - PRs should stay open until merged or if they have not been active for more than 30 days.
     This will help keep the PR queue to a manageable size and reduce noise. Should the PR need
     to stay open (like in the case of a WIP), the `keep open` label can be added.
+    - Before merging a PR, refer to the topic on [Size Labels](#size-labels) below to determine if
+      the PR requires more than one LGTM to merge.
     - If the owner of the PR is listed in `OWNERS`, that user **must** merge their own PRs or explicitly
     request another OWNER do that for them.
     - If the owner of a PR is _not_ listed in `OWNERS`, any maintainer may merge the PR once it is approved.
@@ -320,11 +322,15 @@ The following tables define all label types used for Helm. It is split up by cat
 
 Size labels are used to indicate how "dangerous" a PR is. The guidelines below are used to assign the
 labels, but ultimately this can be changed by the maintainers. For example, even if a PR only makes
-30 lines of changes in 1 file, but it changes key functionality, it will likely be labeled as `size/large`
+30 lines of changes in 1 file, but it changes key functionality, it will likely be labeled as `size/L`
 because it requires sign off from multiple people. Conversely, a PR that adds a small feature, but requires
-another 150 lines of tests to cover all cases, could be labeled as `size/small` even though the number
+another 150 lines of tests to cover all cases, could be labeled as `size/S` even though the number
 lines is greater than defined below.
 
+PRs submitted by a core maintainer, regardless of size, only requires approval from one additional
+maintainer. This ensures there are at least two maintainers who are aware of any significant PRs
+introduced to the codebase.
+
 | Label | Description |
 | ----- | ----------- |
 | `size/XS` | Anything less than or equal to 9 lines ignoring generated files. Only small amounts of manual testing may be required. |