Add pull request manually merge instruction (#13840)

* add pull request command line instructions

* Add pull request manually merge instuction

* Fix styles

* Fix lint

* Move inline style to class file

* add space between merge button and hint text

* Add sentence end charcter

* Change the language file

* adjust secondary bg

* further adjustment

Co-authored-by: silverwind <me@silverwind.io>

web_src/less/_base.less

@@ -99,7 +99,8 @@
   --color-markdown-code-block: #00000008;
   --color-button: #ffffff;
   --color-code-bg: #ffffff;
-  --color-shadow: #00000024;
+  --color-markdown-code-block: #00000010;
+  --color-secondary-bg: #f4f4f4;
 }
 
 :root:lang(ja) {
@@ -1691,6 +1692,11 @@ a.ui.basic.label:hover {
   border-color: var(--color-secondary);
 }
 
+.ui.secondary.segment {
+  background: var(--color-secondary-bg);
+  color: var(--color-text-light);
+}
+
 .ui.attached.header {
   position: relative;
   background: var(--color-box-header);

web_src/less/helpers.less

@@ -1,5 +1,7 @@
 .df { display: flex !important; }
+.di { display: inline !important; }
 .dif { display: inline-flex !important; }
+.dib { display: inline-block !important; }
 .ac { align-items: center !important; }
 .tc { text-align: center !important; }
 .jc { justify-content: center !important; }

web_src/less/themes/theme-arc-green.less

@@ -95,6 +95,7 @@
   --color-button: #353846;
   --color-code-bg: #2a2e3a;
   --color-shadow: #00000060;
+  --color-secondary-bg: #2a2e3a;
 }
 
 /* LineTableTD */
@@ -827,10 +828,6 @@ td.blob-hunk {
   color: #dbdbdb;
 }
 
-.ui.secondary.segment {
-  background: #353945;
-}
-
 .ui.attached.info.message,
 .ui.info.message {
   box-shadow: 0 0 0 1px #4b5e71 inset, 0 0 0 0 transparent;