explore tweaks Round 1 (#7511)

A few small tweaks to the new `explore` command:

1. Rewrote the help text a bit.
    1. I think it's important to mention `:try` up front.
2. Removed the info about `:help foo` because it's currently supported
by very few subcommands
2. Make `exit_esc` default to true. I want to avoid people getting stuck
in `explore` like they get stuck in Vim
3. ~~Always show the help message ("For help type :help") on startup~~
1. The message is small+unobtrusive and I don't this is worth a
configuration item
4. Exit the information view when Escape is pressed
5. General typo+grammar cleanup
    
cc: @zhiburt @fdncred

crates/nu-command/src/viewers/explore.rs

@@ -76,7 +76,7 @@ impl Command for Explore {
         update_config(&mut config, show_index, show_head);
 
         let show_banner = is_need_banner(&config).unwrap_or(true);
-        let exit_esc = is_need_esc_exit(&config).unwrap_or(false);
+        let exit_esc = is_need_esc_exit(&config).unwrap_or(true);
 
         let style = style_from_config(&config);