Add powerline git, LN, lock symbols

Symbols taken from https://github.com/powerline/fontpatcher/blob/develop/fonts/powerline-symbols.sfd

The original symbols use height and widith of approx 1060x2048, so I
modified to be roughly 1000x1000 via:

fontforge -lang=ff -c 'Open($1); SelectAll(); UnlinkReference(); Scale(100, 50); Move(0, 300); Export("svg/%n-%e.svg");' powerline-symbols.sfd

Then I edited by hand to round values to approx 2 significant digits,
and then used a script to convert relative SVG commands such as 'l',
'c', 's' to use only 'M', 'L' and 'C' and used expected format with
comma separators rather than spaces, and divide all values by 1000 to
map into a 1x1 space.

src/browser/renderer/shared/CustomGlyphs.ts

@@ -355,6 +355,12 @@ const enum VectorType {
  * Original symbols defined in https://github.com/powerline/fontpatcher
  */
 export const powerlineDefinitions: { [index: string]: IVectorShape } = {
+  // Git branch
+  '\u{E0A0}': { d: 'M.3,1 L.03,1 L.03,.88 C.03,.82,.06,.78,.11,.73 C.15,.7,.2,.68,.28,.65 L.43,.6 C.49,.58,.53,.56,.56,.53 C.59,.5,.6,.47,.6,.43 L.6,.27 L.4,.27 L.69,.1 L.98,.27 L.78,.27 L.78,.46 C.78,.52,.76,.56,.72,.61 C.68,.66,.63,.67,.56,.7 L.48,.725 C.42,.745,.38,.765,.35,.785 C.32,.805,.31,.845,.31,.885 L.31,1.005 M.3,.5 L.03,.59 L.03,.09 L.3,.09 L.3,.655', type: VectorType.FILL },
+  // L N
+  '\u{E0A1}': { d: 'M.7,.4 L.7,.47 L.2,.47 L.2,.03 L.355,.03 L.355,.4 L.705,.4 M.7,.5 L.86,.5 L.86,.95 L.69,.95 L.44,.66 L.46,.86 L.46,.95 L.3,.95 L.3,.49 L.46,.49 L.71,.78 L.69,.565 L.69,.5', type: VectorType.FILL },
+  // Lock
+  '\u{E0A2}': { d: 'M.25,.94 C.16,.94,.11,.92,.11,.87 L.11,.53 C.11,.48,.15,.455,.23,.45 L.23,.3 C.23,.25,.26,.22,.31,.19 C.36,.16,.43,.15,.51,.15 C.59,.15,.66,.16,.71,.19 C.77,.22,.79,.26,.79,.3 L.79,.45 C.87,.45,.91,.48,.91,.53 L.91,.87 C.91,.92,.86,.94,.77,.94 L.24,.94 M.53,.2 C.49,.2,.45,.21,.42,.23 C.39,.25,.38,.27,.38,.3 L.38,.45 L.68,.45 L.68,.3 C.68,.27,.67,.25,.64,.23 C.61,.21,.58,.2,.53,.2 M.58,.82 L.58,.66 C.63,.65,.65,.63,.65,.6 C.65,.58,.64,.57,.61,.56 C.58,.55,.56,.54,.52,.54 C.48,.54,.46,.55,.43,.56 C.4,.57,.39,.59,.39,.6 C.39,.63,.41,.64,.46,.66 L.46,.82 L.57,.82', type: VectorType.FILL },
   // Right triangle solid
   '\u{E0B0}': { d: 'M0,0 L1,.5 L0,1', type: VectorType.FILL, rightPadding: 2 },
   // Right triangle line