Add subscript to issue templates (#13193)

#### Description
As part of open-telemetry/sig-end-user#11,
this adds a subscript paragraph to all issue templates to help end-users
and other community members interact with issues.

This change is accompanied by the changes in the maintainer guide
proposed in open-telemetry/community#2778, and
the changes to the website in
open-telemetry/opentelemetry.io#7088 giving
users more information about issue participation

The major caveat of this PR is the necessity of using the `dropdown`
element in issue forms. As covered in this [feedback discussion
topic](https://github.com/orgs/community/discussions/63402#discussioncomment-10341167),
it is not possible to create `markdown` elements that render on the
resulting issue body. As such, the only possibilities are a checkbox, a
dropdown, or some form of pre-filled input text that would be even more
confusing.

Working version can be seen in
danielgblanco/opentelemetry-collector-contrib#6
with the issue form being rendered as
https://github.com/danielgblanco/opentelemetry-collector-contrib/issues/new?template=bug_report.yaml

Author: danielgblanco

.github/ISSUE_TEMPLATE/bug_report.yaml

@@ -128,4 +128,10 @@ body:
     attributes:
       label: Additional context
       description: Any additional information you think may be relevant to this issue.
-
+  - type: dropdown
+    attributes:
+      label: Tip
+      description: This element is static, used to render a helpful sub-heading for end-users and community members to help prioritize issues. Please leave as is.
+      options:
+        - <sub>[React](https://github.blog/news-insights/product-news/add-reactions-to-pull-requests-issues-and-comments/) with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding `+1` or `me too`, to help us triage it. Learn more [here](https://opentelemetry.io/community/end-user/issue-participation/).</sub>
+      default: 0

.github/ISSUE_TEMPLATE/feature_request.yaml

@@ -75,3 +75,10 @@ body:
     attributes:
       label: Additional context
       description: Add any other context or screenshots about the feature request here.
+  - type: dropdown
+    attributes:
+      label: Tip
+      description: This element is static, used to render a helpful sub-heading for end-users and community members to help prioritize issues. Please leave as is.
+      options:
+        - <sub>[React](https://github.blog/news-insights/product-news/add-reactions-to-pull-requests-issues-and-comments/) with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding `+1` or `me too`, to help us triage it. Learn more [here](https://opentelemetry.io/community/end-user/issue-participation/).</sub>
+      default: 0

.github/ISSUE_TEMPLATE/other.yaml

@@ -59,3 +59,10 @@ body:
       description: A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
     validations:
       required: true
+  - type: dropdown
+    attributes:
+      label: Tip
+      description: This element is static, used to render a helpful sub-heading for end-users and community members to help prioritize issues. Please leave as is.
+      options:
+        - <sub>[React](https://github.blog/news-insights/product-news/add-reactions-to-pull-requests-issues-and-comments/) with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding `+1` or `me too`, to help us triage it. Learn more [here](https://opentelemetry.io/community/end-user/issue-participation/).</sub>
+      default: 0

.github/ISSUE_TEMPLATE/stabilization.md

@@ -23,3 +23,5 @@ Please also make sure to publicly announce our intent to stabilize the module on
 To help other people verify the above criteria, please link to the announcement and other links used to complete the above in a comment on this issue.
 
 Once all criteria are met, close this issue by moving this module to the `stable` module set.
+
+<sub>**Tip**: [React](https://github.blog/news-insights/product-news/add-reactions-to-pull-requests-issues-and-comments/) with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding `+1` or `me too`, to help us triage it. Learn more [here](https://opentelemetry.io/community/end-user/issue-participation/).</sub>

.github/ISSUE_TEMPLATE/vote.md

@@ -59,3 +59,5 @@ For closing the vote:
 - [ ] At least one-third of the stakeholders have voted.
 - [ ] The "Voting options" and "Result" sections have been updated reflecting the votes casted.
 - [ ] The RFC has been updated reflecting the votes casted.
+
+<sub>**Tip**: [React](https://github.blog/news-insights/product-news/add-reactions-to-pull-requests-issues-and-comments/) with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding `+1` or `me too`, to help us triage it. Learn more [here](https://opentelemetry.io/community/end-user/issue-participation/).</sub>