fix typos in navigation

mkdocs.yml

@@ -16,11 +16,11 @@ nav:
   - Home: index.md
   - Test:
     - Test site: testing-nav/test-site.md
-  - Technical documentation:
-    - Instalation and System requirements:
+  - Technical documentation: 
+    - Installation and system requirements:
       - Overview: technical-documentation/installation/overview.md
-      - Front-end instalation: technical-documentation/installation/front-README.md
-      - Back-end instalation: technical-documentation/installation/back-README.md
+      - Front-end installation: technical-documentation/installation/front-README.md
+      - Back-end installation: technical-documentation/installation/back-README.md
     - System architecture:
       - Overview: technical-documentation/architecture/overview.md
       - Definition documentation: technical-documentation/architecture/definitions.md
@@ -29,8 +29,8 @@ nav:
       - Authentization: technical-documentation/security-auth.md
     - API Documentation:
       - Overview: technical-documentation/api/overview.md
-      - Graphql Documentaion: technical-documentation/api/graphql-docs.md
-      - Swagger REST documentaion: technical-documentation/api/swagger-docs.md
+      - Graphql Documentation: technical-documentation/api/graphql-docs.md
+      - Swagger REST documentation: technical-documentation/api/swagger-docs.md 
     - Changelog on backend: technical-documentation/CHANGELOG.md
 
 markdown_extensions: