chore: add changeset files

Signed-off-by: Camila Belo <camilaibs@gmail.com>

.changeset/flat-ducks-buy.md

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+---
+'@backstage/plugin-search-backend-node': patch
+---
+
+Fix highlighting for non-string fields on the `Lunr` search engine implementation.

.changeset/giant-cycles-end.md

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+---
+'@backstage/plugin-stack-overflow-backend': patch
+---
+
+Migrate package to the new Frontend system, the new module is distributed with a `/alpha` subpath.

.changeset/mean-fans-cough.md

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+---
+'@backstage/plugin-search': patch
+---
+
+Add Stack Overflow type to the default alpha search page extension types filter.

.changeset/nice-pillows-poke.md

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+---
+'@backstage/plugin-stack-overflow': patch
+---
+
+Migrate package to the new Backend system, the new module is distributed with a `/alpha` subpath.