Add issue template for new language

.gitea/issue_template/config.yaml

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+blank_issues_enabled: true
+contact_links:
+  - name: Join the translators server
+    about: Got a question or suggestion? You will receive a faster response here.
+    url: "https://rvlt.gg/5dHVyTjb"

.gitea/issue_template/new_language.yaml

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+name: Add a new language
+about: Request a new language to be added
+title: "Add language: <language>"
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Please fill out the issue title as well as the fields below!
+  - type: input
+    id: lang-name
+    attributes:
+      label: Language name
+      description: The English name of the language
+      placeholder: German
+    validations:
+      required: true
+  - type: input
+    id: lang-name-localised
+    attributes:
+      label: Localised language name
+      description: The translated name of the language
+      placeholder: Deutsch
+    validations:
+      required: true
+  - type: input
+    id: lang-code
+    attributes:
+      label: Language code
+      description: 2-letter language code
+      placeholder: de
+    validations:
+      required: true
+  - type: input
+    id: weblate-user
+    attributes:
+      label: Weblate profile
+      description: Please provide your Weblate username or a link to your profile if you want to be added as a maintainer 
+      placeholder: "https://weblate.insrt.uk/user/lea/"
+    validations:
+      required: false
+  - type: checkbox
+    id: add-as-maintainer
+    label: Language maintainer
+    description: |
+      Only check this if you've made substantial contributions to Revolt's translations in this language or are already elected as language maintainer there.
+      If you do, make sure to provide your Weblate profile above!
+    options:
+      - label: Add me as language maintainer
+  - type: textarea
+    label: Additional information
+    placeholder: Is there anything else you would like us to know?