Add glossary to docs

This commit adds a glossary to the documentation, providing definitions for key
terms used in the Yorkie project and community. This addition will help users
better understand the terminology used in the project.

docs/glossary.mdx

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+---
+title: 'Glossary'
+order: 100
+---
+
+## Glossary
+
+This words are used in the Yorkie project and the community.
+
+| Category | Word | Description |
+| ---- | ---- | ----------- |
+| Core | Yorkie | An open-source document store for building real-time collaborative applications. Sometimes it refers to the main repository. |
+| Core | Client | An regular client that communicates with the Yorkie server, synchronizing document changes for real-time collaboration. |
+| Core | Server | The central component that manages documents, stores changes, and facilitates communication between clients. |
+| Core | Project | A logical grouping of documents and clients, allowing multiple independent services within a single Yorkie installation. |
+| Core | Document | The primary data structure in Yorkie. It contains a presence and a root. |
+| Core | Presence | A data structure representing a user's current state within a document (e.g., cursor position, selection). |
+| Core | Root | The main JSON-like data structure(CRDT) within a document that can be shared and edited by multiple users. |
+| Core | Change | A representation of modifications made to a document, created by calling Document.Update. |
+| Network | PushPullChanges | An API for bidirectional synchronization of changes between clients and the server. |
+| Network | Checkpoint | A mechanism for tracking the synchronization state between clients and the server, consisting of ServerSeq and ClientSeq. |
+| Network | Housekeeping | A maintenance process that cleans up unnecessary data on the server. |
+| CRDT | CRDT Element | A data structure representing a CRDT element, analogous to an Element in the DOM. |
+| CRDT | CRDT Node | A single node within a CRDT element(Text, Tree). |
+| CRDT | Tombstone | A marker for a deleted node in the CRDT. |
+| CRDT | Garbage Collection | The process of removing nodes marked as tombstones to optimize storage and performance. |