update instructions for 2.0.0

UPDATE.md

@@ -1,3 +1,75 @@
+# Updating
+
+## 1.7.x -> 2.0.0
+
+### prerequisites
+
+1. create an export of your data in **Admin -> Import/Export -> New Export** and download it in case something breaks  
+2. install postgresql (if you don't have it): [postgresql.org](https://www.postgresql.org/download/)  
+3. install pgloader: [pgloader.readthedocs.io](https://pgloader.readthedocs.io/en/latest/install.html)  
+4. start postgresql  
+
+### performing the upgrade
+
+1. create a new postgresql user:
+```sql
+CREATE USER "<username>" WITH PASSWORD "<password>";
+```
+1. create a new postgresql database:
+```sql
+CREATE DATABASE "<db name>" OWNER "<db user>";
+```
+2. run pgloader:
+```sh
+pgloader mysql://old_user:old_password@127.0.0.1/old_catask pgsql://new_user:new_password@127.0.0.1/new_catask
+```
+
+3. pull the update: `git pull`
+
+4. make the following changes in your config.json file:
+```diff
+	...
+    "accessibility": {
+        "font": "default",
+        "userway": {
+            "enabled": false,
+            "account": "p3mmiCKHVO"
+        }
+    },
++	"languages": {
++		"default": "en_US",
++		"allowChanging": true
++	},
+    "style": {
+        "accentLight": "#b86565",
+        "accentDark": "#b86565",
+        "bgLight": "#ffffff",
+        "bgDark": "#202020",
+        "navStyle": "pills",
+        "tintColors": true,
+        "infoBoxLayout": "row",
+        "homepageLayout": "catask",
+        "navIcons": true,
+        "navIconsOnly": false,
++		"customCss": "",
++		"useCustomCss": false,
++		"overrideBaseStyles": false,
++		"overrideCatAskStyles": false,
++		"cardStyle": "compact"
+    },
+	...
+	"ntfy": {
+		"enabled": false,
+		"host": "https://ntfy.sh",
+		"user": "",
+		"pass": "",
+		"topic": ""
+	},
++	"themeStoreUrl": "https://themes.catask.mystie.dev",
++	"username": ""
+    ...
+```
+
 ## 1.7.0 -> 1.7.x
 pull the update: `git pull`  
 make the following changes in your config.json file: