Add install documentation (#9)

Author: eshlox

README.md

@@ -64,6 +64,7 @@ dvm rm <name> [--force]
 
 Docs:
 
+- [Install](docs/install.md)
 - [Dependencies](docs/dependencies.md)
 - [Config](docs/config.md)
 - [Create VMs](docs/create.md)

docs/README.md

@@ -1,5 +1,6 @@
 # Docs
 
+- [Install](install.md)
 - [Dependencies](dependencies.md)
 - [Config](config.md)
 - [Create VMs](create.md)

docs/install.md

@@ -0,0 +1,82 @@
+# Install
+
+Install DVM by cloning the repository and running `install.sh`. The installer creates a
+symlink to `bin/dvm`, so the checkout remains the DVM core.
+
+## Requirements
+
+```bash
+brew install lima
+```
+
+Make sure the install prefix is on your `PATH`:
+
+```bash
+mkdir -p "$HOME/.local/bin"
+```
+
+## Stable Install
+
+Use a signed release tag when installing for regular use:
+
+```bash
+git clone https://github.com/eshlox/dvm.git "$HOME/.local/share/dvm-core"
+cd "$HOME/.local/share/dvm-core"
+git fetch --tags --force
+git tag -v vX.Y.Z
+git checkout --detach vX.Y.Z
+./install.sh --init
+```
+
+If tag verification fails, do not install that version.
+
+## Development Install
+
+Use `main` only for development or testing:
+
+```bash
+git clone https://github.com/eshlox/dvm.git "$HOME/.local/share/dvm-core"
+cd "$HOME/.local/share/dvm-core"
+./install.sh --init
+```
+
+This creates:
+
+```text
+~/.local/bin/dvm -> ~/.local/share/dvm-core/bin/dvm
+```
+
+## Custom Name Or Prefix
+
+```bash
+./install.sh --name dvm-dev --prefix "$HOME/bin" --init
+```
+
+## Verify
+
+```bash
+dvm help
+dvm init
+```
+
+## Update DVM
+
+For a signed release:
+
+```bash
+cd "$HOME/.local/share/dvm-core"
+git fetch --tags --force
+git tag -v vX.Y.Z
+git checkout --detach vX.Y.Z
+./install.sh
+```
+
+For a development checkout:
+
+```bash
+cd "$HOME/.local/share/dvm-core"
+git pull --ff-only
+./install.sh
+```
+
+DVM intentionally does not support remote install commands like `curl | sh`.