Update issue templates (#13970)

* Update issue templates

Added labels to all the templates as well as descriptions.

Next step:
- Mandatory fields.

* Update .github/ISSUE_TEMPLATE/bug_report.md

Co-authored-by: matheusaaguiar <95899911+matheusaaguiar@users.noreply.github.com>

* Update .github/ISSUE_TEMPLATE/documentation_issue.md

Co-authored-by: matheusaaguiar <95899911+matheusaaguiar@users.noreply.github.com>

---------

Co-authored-by: matheusaaguiar <95899911+matheusaaguiar@users.noreply.github.com>

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,5 +1,10 @@
 ---
 name: Bug Report
+about: Problems, deficiencies, inaccuracies or crashes discovered on Solidity.
+title: ''
+labels: 'bug :bug:'
+assignees: ''
+
 ---
 
 <!--## Prerequisites

.github/ISSUE_TEMPLATE/documentation_issue.md

@@ -1,5 +1,10 @@
 ---
 name: Documentation Issue
+about: Corrections, improvements or requests for new content on Solidity's documentation.
+title: ''
+labels: 'documentation :book:'
+assignees: ''
+
 ---
 
 ## Page

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,5 +1,11 @@
 ---
 name: Feature Request
+about: Ideas, comments or messages asking for a particular functionality to be added
+  to Solidity.
+title: ''
+labels: feature
+assignees: ''
+
 ---
 
 <!--## Prerequisites