Clean up issue filing template

Clean up typos and make the descriptions clearer. Remove some
unnecessary checkboxes and make some fields more specific to MacVim.
Also make it clear that Vim issues should be filed upstream.

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -10,6 +10,8 @@ body:
         Thanks for reporting issues of MacVim!
 
         If you want to report a security issue, instead of reporting it here publicly, please disclose it using the steps listed at https://github.com/macvim-dev/macvim/security/policy.
+
+        For general Vim issues that are not specific to MacVim, please file them at https://github.com/vim/vim.
         
         To make it easier for us to help you please enter detailed information below.
   - type: textarea
@@ -30,56 +32,48 @@ body:
       required: true
   - type: input
     attributes:
-      label: Version of Vim and architecture
+      label: Version of MacVim
       description: >
-        Including patch level, use ":version" to see it [e.g. 8.2.1234, GUI, arm64]
-    validations:
-      required: true
-  - type: textarea
-    attributes:
-      label: Environment
-      description: >
-        OS and architecture [e.g. Big Sur, arm64], terminal [e.g. Apple Terminal/iTerm], value of $TERM, shell [e.g. zsh 5.8]; anything that might matter
-      placeholder: |
-        Operating system:
-        Terminal:
-        Value of $TERM:
-        Shell:
+        MacVim release number (e.g. r181). Use "About MacVim" to find out which one you are using. If building manually from source, provide the Git commit hash instead (e.g. a4466fe3b695).
     validations:
       required: true
   - type: input
     attributes:
-      label: How MacVim was installed
+      label: MacVim installation method
       description: >
-        MacVim has been downloaded from GitHub, installed via Homebrew, MacPorts or builed from git
+        Was MacVim downloaded from GitHub release, installed via Homebrew / Homebrew Cask / MacPorts, or built from source manually?
+  - type: textarea
+    attributes:
+      label: Environment
+      description: >
+        macOS version (e.g. macOS 15.3.2 Sequoia), Mac type (e.g. MacBook Air M2), terminal (e.g. Apple Terminal/iTerm); anything that might matter
+      placeholder: |
+        macOS version:
+        Mac:
+        Terminal:
+    validations:
+      required: true
   - type: textarea
     attributes:
       label: Logs and stack traces
       placeholder: Insert log or other text here (if necessary)
       render: shell
-  - type: input
+  - type: textarea
     attributes:
-      label: Vim configuration where issue is reproducable
-      description: 'e.g. link to your vimrc configuration: url to file/gist/repo..'
+      label: Vim and MacVim configuration where issue is reproducable
+      description: Provide a link to vimrc and/or MacVim settings (see https://github.com/macvim-dev/macvim/wiki/Reporting-an-Issue for how to obtain it).
   - type: checkboxes
     attributes:
-      label: Issue has been tested with given configuration
-      description: This will help us to narrow down the problem more quickly
+      label: How was MacVim launched?
+      description: Different ways of opening MacVim can have an impact on the behavior.
       options:
-        - label: by running MacVim.app from GUI macOS interface
-        - label: by running vim/gvim/etc installed by MacVim
-        - label: by running other versions of vim (e.g. /usr/bin/vim)
+        - label: by launching MacVim.app in macOS (by using the Dock, Spotlight, or the `open` command)
+        - label: by running mvim/gvim in the terminal
   - type: checkboxes
     attributes:
-      label: Issue has been tested with no configuration
-      description: This will help us to narrow down the problem more quickly
+      label: Issue has been tested with clean configuration
+      description: Running MacVim and Vim with clean configurations allow us to narrow down whether this is a configuration issue.
       options:
-        - label: by running `mvim --clean` (or `gvim`, supplied by MacVim distribution)
+        - label: by running `mvim --clean` (or `gvim`, supplied by MacVim distribution). You can also use the File → "New Clean Window" menu item within MacVim.
         - label: by running `vim --clean` (in terminal, supplied by MacVim distribution)
         - label: by running `vim --clean` (in terminal, other suppliers, e.g. /usr/bin/vim)
-  - type: checkboxes
-    attributes:
-      label: Other conditions
-      description: This will help us to narrow down the problem more quickly
-      options:
-        - label: The both Homebrew packages "vim" and "macvim" are installed