Added powerline theme (#23)

* Added a powerline theme

Credit: Took some help from lightline powerline theme

* Updated THEMES.md

* Small tweek to colors

* swaped onedark and powerline in THEMES.md

THEMES.md

@@ -26,3 +26,10 @@ All available themes are only best effort ports by myself/ other users. If you f
 ![insert](https://user-images.githubusercontent.com/41551030/103468174-cdc99b00-4d56-11eb-8723-fd817ff06404.png)
 ![visual](https://user-images.githubusercontent.com/41551030/103468184-ea65d300-4d56-11eb-99e2-73cb649ab679.png)
 ![replace](https://user-images.githubusercontent.com/41551030/103468213-07020b00-4d57-11eb-9b66-5061de556f44.png)
+
+### powerline
+![normal](https://user-images.githubusercontent.com/13149513/103506288-8fcb9480-4e86-11eb-97f8-3768a34188fd.jpg)
+![insert](https://user-images.githubusercontent.com/13149513/103506295-978b3900-4e86-11eb-8eca-d31514c66275.jpg)
+![visual](https://user-images.githubusercontent.com/13149513/103506318-a40f9180-4e86-11eb-85fd-153d6de2a62f.jpg)
+![command](https://user-images.githubusercontent.com/13149513/103506333-aa057280-4e86-11eb-8098-422eca99c23a.jpg)
+![replace](https://user-images.githubusercontent.com/13149513/103506349-af62bd00-4e86-11eb-9f11-bd6a56214fa3.jpg)

lua/lualine/themes/powerline.lua

@@ -0,0 +1,88 @@
+local M = {  }
+
+local Colors = {
+  white          = '#ffffff',
+  darkestgreen   = '#005f00',
+  brightgreen    = '#afdf00',
+  darkestcyan    = '#005f5f',
+  mediumcyan     = '#87dfff',
+  darkestblue    = '#005f87',
+  darkred        = '#870000',
+  brightred      = '#df0000',
+  brightorange   = '#ff8700',
+  gray1          = '#262626',
+  gray2          = '#303030',
+  gray4          = '#585858',
+  gray5          = '#606060',
+  gray7          = '#9e9e9e',
+  gray10         = '#f0f0f0',
+}
+
+M.normal = {
+  a = {
+    fg = Colors.darkestgreen, 
+    bg = Colors.brightgreen,
+  },
+  b = {
+    fg = Colors.gray10,
+    bg = Colors.gray5,
+  },
+  c = {
+    fg = Colors.gray7,
+    bg = Colors.gray2,
+  },
+}
+
+M.insert = {
+  a = {
+    fg = Colors.darkestcyan,
+    bg = Colors.white,
+  },
+  b = {
+    fg = Colors.darkestcyan,
+    bg = Colors.mediumcyan,
+  },
+  c = {
+    fg = Colors.mediumcyan,
+    bg = Colors.darkestblue,
+  },
+}
+
+
+M.visual = {
+  a = {
+    fg = Colors.darkred,
+    bg = Colors.brightorange,
+  },
+  b = M.normal.b,
+  c = M.normal.c,
+}
+
+M.replace = {
+  a = {
+    fg = Colors.white,
+    bg = Colors.brightred,
+  },
+  b = M.normal.b,
+  c = M.normal.c,
+}
+
+M.command = M.normal  
+M.terminal = M.normal
+
+M.inactive = {
+  a = {
+    fg = Colors.gray1,
+    bg = Colors.gray5,
+  },
+  b = {
+    fg = Colors.gray1,
+    bg = Colors.gray5,
+  },
+  c = {
+    bg = Colors.gray1,
+    fg = Colors.gray5,
+  },
+}
+
+return M