docs: add sunshine creds (#11)

Author: ReenigneArcher

.markdownlint.yaml

@@ -75,7 +75,7 @@ MD013:
   # Number of characters for headings
   heading_line_length: 80
   # Number of characters for code blocks
-  code_block_line_length: 80
+  code_block_line_length: 120
   # Include code blocks
   code_blocks: true
   # Include tables

docs/sunshine/creds.md

@@ -0,0 +1,32 @@
+# Forgotten Credentials
+
+If you forgot your credentials to the web UI, try this.
+
+## General
+
+```bash
+sunshine --creds {new-username} {new-password}
+```
+
+## AppImage (Linux)
+
+```bash
+./sunshine.AppImage --creds {new-username} {new-password}
+```
+
+## Flatpak (Linux)
+
+### From github.com/LizardByte releases
+
+```bash
+flatpak run --command=sunshine dev.lizardbyte.Sunshine --creds {new-username} {new-password}
+```
+
+### From Flathub
+
+```bash
+flatpak run --command=sunshine dev.lizardbyte.app.Sunshine --creds {new-username} {new-password}
+```
+
+This information is also available in our
+[troubleshooting docs](https://docs.lizardbyte.dev/projects/sunshine/en/latest/troubleshooting/general.html#forgotten-credentials)