Add example links to exploring section (#298)

- Moves example WARC files to /site/examples
- Adds example link for full text search
- Adds example link for searching resources
- Updates example docs link on the app homepage, sends to the project
showcase section
- Link fix
- .gitignore update
---------

Co-authored-by: Ilya Kreymer <ikreymer@gmail.com>

.gitignore

@@ -1,7 +1,7 @@
 *.har
 *.warc
 *.warc.gz
-!examples/*.warc
+!site/examples/*.warc
 **/node_modules
 yarn-error.log
 coverage/
@@ -9,7 +9,7 @@ coverage/
 **/.DS_Store
 **/.sass-cache/
 **/__pycache__/
-_genhtml/
+mkdocs/_genhtml/
 dist/
 plugins-*/
 site/sw.js