Fix help menu icon colour and let it scroll

sass/_chatbox.scss

@@ -240,8 +240,17 @@
             }
 
             .chat-content__help {
+                border-top: 1px solid var(--chat-head-color);
+                max-height: 100%;
+                .close-chat-help {
+                    svg {
+                        fill: var(--chat-head-color);
+                    }
+                }
+
                 converse-chat-help {
-                    border-top: 1px solid var(--chat-head-color);
+                    height: 100%;
+                    overflow-y: auto;
                     display: block;
                     padding: 0.5em 0;
                 }

sass/_chatrooms.scss

@@ -177,12 +177,10 @@
                         height: 100%;
                     }
                     .chat-content__help {
-                        converse-chat-help {
-                            border-top: 1px solid var(--chatroom-head-bg-color);
-                        }
+                        border-top: 1px solid var(--chatroom-head-bg-color);
                         .close-chat-help {
                             svg {
-                                fill: 1px solid var(--chatroom-head-bg-color) !important;
+                                fill: var(--chatroom-head-bg-color);
                             }
                         }
                     }

src/components/help_messages.js

@@ -1,7 +1,7 @@
 import './icons.js';
 import xss from 'xss/dist/xss';
 import { CustomElement } from './element.js';
-import { _converse, api } from '@converse/headless/converse-core';
+import { api } from '@converse/headless/converse-core';
 import { html } from 'lit-element';
 import { unsafeHTML } from 'lit-html/directives/unsafe-html.js';
 
@@ -18,13 +18,11 @@ export default class ChatHelp extends CustomElement {
     }
 
     render () {
-        const icon_color = this.chat_type === _converse.CHATROOMS_TYPE ? 'var(--chatroom-head-bg-color)' : 'var(--chat-head-color)';
         const isodate = (new Date()).toISOString();
         return [
             html`<converse-icon class="fas fa-times close-chat-help"
                     @click=${this.close}
                     path-prefix="${api.settings.get("assets_path")}"
-                    color="${icon_color}"
                     size="1em"></converse-icon>`,
             ...this.messages.map(m => this.renderHelpMessage({
                 isodate,