How to have a custom iPhone keyboard?

1. So basically I'm like the biggest novice to Xcode and all I want to do is have a custom iPhone keyboard so i can have a keyboard layout that is able to type certain special characters without even having to hold down on a key. Basically just i can type everything like the usual US English QWERTY keyboard but each letter is bold serif (so it's pretty much "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890" to "𝐚𝐛𝐜𝐝𝐞𝐟𝐠𝐡𝐢𝐣𝐤𝐥𝐦𝐧𝐨𝐩𝐪𝐫𝐬𝐭𝐮𝐯𝐰𝐱𝐲𝐳𝐀𝐁𝐂𝐃𝐄𝐅𝐆𝐇𝐈𝐉𝐊𝐋𝐌𝐍𝐎𝐏𝐐𝐑𝐒𝐓𝐔𝐕𝐖𝐗𝐘𝐙𝟏𝟐𝟑𝟒𝟓𝟔𝟕𝟖𝟗𝟎"). I did a little research and found that to do this I would need to use Xcode, which I already had on my MacBook, but I have never really used Xcode. Like I found the forum to use Xcode to do this project (I think, it might be wrong but it's Creating a custom keyboard | Apple Developer Documentation), but the VERY FIRST STEP I'm running into problems. The instructions tell me to "Choose File > New > Target", but when I do that "Target" is grayed out and I can't figure it out. So what I'm asking for is to figure out how to have a custom keyboard (Standard US QWERTY keyboard but 𝐛𝐨𝐥𝐝 𝐬𝐞𝐫𝐢𝐟) on my iPhone in the easiest way possible. I would like something that doesn't use Xcode, but this seems like the only path I can take. Can someone help me?

[Re-Titled by Moderator]