Add comprehensive documentation with i18n support (EN/BG)

- Add docs/ folder with English (en/) and Bulgarian (bg/) documentation
- Create index.md with language switching and links
- English docs: installation, quickstart, architecture, baraql, storage,
  schema, lsm, btree, vector, graph, fts, columnar, transactions,
  distributed, protocol, udf, api-binary, api-http, api-websocket
- Bulgarian docs: installation, quickstart, architecture, baraql,
  schema, lsm, btree, vector, graph, fts, transactions, distributed
- Update README license to BSD 3-Clause
- Add LICENSE file with BSD 3-Clause text

docs/bg/schema.md

@@ -0,0 +1,40 @@
+# Схема на BaraDB
+
+BaraDB използва схема с типове, наследяване и автоматични миграции.
+
+## Дефиниране на Типове
+
+```nim
+import barabadb/schema/schema
+
+var s = newSchema()
+
+let person = newType("Person")
+person.addProperty("name", "str", required = true)
+person.addProperty("age", "int32")
+s.addType("default", person)
+```
+
+## Наследяване на Типове
+
+```nim
+let employee = newType("Employee")
+employee.setBases(@["Person"])
+employee.addProperty("department", "str")
+s.addType("default", employee)
+
+let resolved = s.resolveInheritance(employee)
+```
+
+## Типове Полета
+
+| Тип | Описание |
+|-----|---------|
+| `str` | Низ |
+| `int32` | 32-битово цяло число |
+| `int64` | 64-битово цяло число |
+| `float32` | 32-битов float |
+| `float64` | 64-битов float |
+| `bool` | Булева стойност |
+| `datetime` | Дата/час |
+| `bytes` | Двоични данни |